Filter System And Method For Imaging A Subject

ABSTRACT

A method and system is disclosed for acquiring image data of a subject. The image data can be collected with an imaging system with at least two different energy characteristics. The image data can be reconstructed using reconstruction techniques.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. patent application Ser. No.16/893,003 filed on Jun. 4, 2020, which is a Divisional of U.S. patentapplication Ser. No. 15/498,921 filed on Apr. 27, 2017. This applicationalso includes subject matter similar to that disclosed in U.S. patentapplication Ser. No. 15/498,865 and U.S. patent application Ser. No.15/498,964, both concurrently filed on Apr. 27, 2017. The entiredisclosures of each of the above applications are incorporated herein byreference.

FIELD

The present disclosure relates to imaging a subject, and particularly toa system to acquire image data with a duel energy imaging system.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

A subject, such as a human patient, may select or be required to undergoa surgical procedure to correct or augment an anatomy of the subject.The augmentation of the anatomy can include various procedures, such asmovement or augmentation of bone, insertion of an implant (i.e. animplantable device), or other appropriate procedures. A surgeon canperform the procedure on the subject with images of the subject that canbe acquired using imaging systems such as a magnetic resonance imaging(MRI) system, computed tomography (CT) system, fluoroscopy (e.g. C-Armimaging systems), or other appropriate imaging systems.

Images of a subject can assist a surgeon in performing a procedureincluding planning the procedure and performing the procedure. A surgeonmay select a two dimensional image or a three dimensional imagerepresentation of the subject. The images can assist the surgeon inperforming a procedure with a less invasive technique by allowing thesurgeon to view the anatomy of the subject without removing theoverlying tissue (including dermal and muscular tissue) when performinga procedure.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

According to various embodiments, a system to acquire image data of asubject, such as a living patient (e.g. a human patient), with animaging system may use a plurality of energies. Further, enhancedcontrast imaging can include a contrast agent with the plurality ofenergies or without. An imaging system having the plurality of energiesmay include a first energy source with a first energy parameters and asecond energy source with a second energy parameters to energize asource. Further, the imaging system may include a plurality of sources(each source may have the same trajectory or path), wherein each sourceincludes one or more different energy characteristics.

The imaging system can also include a pump operable to inject a contrastagent into the subject based on an instruction. A controller can be incommunication with both the imaging system and the pump to provide theinstruction to the pump to inject the contrast agent. The imaging systemcan communicate with the pump through the controller regarding timing ofthe injection of a contrast agent into the patient and is furtheroperable to acquire image data based upon the timing of the injection ofthe contrast agent and/or the clinical procedure.

The imaging system may further include one or more filters to ensure,and/or assist in ensuring, appropriate or selected separation betweenthe first energy characteristics and the second energy characteristics.The first energy characteristics may be selected to provide a firstx-ray energy spectra with the first energy characteristics and a secondx-ray energy spectra at the second energy characteristics. The filtermay be provided at a selected time to assist in ensuring appropriate orselected spectra for imaging the subject, such as eliminating possibleor actual overlap of the x-ray energy spectra.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is an environmental view of an imaging system in an operatingtheatre;

FIG. 2 is a detailed schematic view of an imaging system with a dualenergy source system;

FIG. 3 is a detailed view of a filter assembly according to variousembodiments;

FIG. 4 is a detailed view of a filter assembly, according to variousembodiments;

FIG. 5 is a detailed view of a filter assembly, according to variousembodiments;

FIG. 6 is a perspective view of a drive assembly for the filter assemblyillustrated in FIG. 5;

FIG. 7 is a flowchart of a synchronization method;

FIG. 8 is a detailed view of a filter assembly, according to variousembodiments;

FIG. 9 is a view of a multiple-axis collimator assembly, according tovarious embodiments;

FIG. 10A is a first perspective view of a X and Y axis selectionassembly for the multiple-axis collimator assembly, according to variousembodiments;

FIG. 10B is a second perspective view of the X and Y axis selectionassembly of FIG. 10A for the multiple-axis collimator assembly,according to various embodiments;

FIG. 11 is a plan view of a X and Y axis selection assembly for themultiple-axis collimator assembly, according to various embodiments;

FIG. 12 is a perspective view of a X and Y axis selection assembly forthe multiple-axis collimator assembly, according to various embodiments;

FIG. 13 a detailed view of a multiple filter filter-assembly, accordingto various embodiments; and

FIG. 14 a detailed view of a multiple filter filter-assembly, accordingto various embodiments.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

With reference to FIG. 1, in an operating theatre or operating room 10,a user, such as a surgeon 12, can perform a procedure on a subject, suchas a patient, 14. In performing the procedure, the user 12 can use animaging system 16 to acquire image data of the patient 14 to allow aselected system to generate or create images to assist in performing aprocedure. A model (such as a three-dimensional (3D) image) can begenerated using the image data and displayed as an image 18 on a displaydevice 20. The display device 20 can be part of and/or connected to aprocessor system 22 that includes an input device 24, such as akeyboard, and a processor 26 which can include one or more processors ormicroprocessors incorporated with the processing system 22 along withselected types of non-transitory and/or transitory memory. A connection28 can be provided between the processor 26 and the display device 20for data communication to allow driving the display device 20 to displayor illustrate the image 18.

The imaging system 16 can include an O-Arm® imaging system sold byMedtronic Navigation, Inc. having a place of business in Louisville,Colo., USA. The imaging system 16, including the O-Arm® imaging system,or other appropriate imaging systems may be in use during a selectedprocedure, such as the imaging system described in U.S. Patent App.Pubs. 2012/0250822, 2012/0099772, and 2010/0290690, all incorporatedherein by reference.

The imaging system 16, when, for example, including the O-Arm® imagingsystem, may include a mobile cart 30 that includes a controller and/orcontrol system 32. The control system may include a processor 33 a and amemory 33 b (e.g. a non-transitory memory). The memory 33 b may includevarious instructions that are executed by the processor 33 a to controlthe imaging system, including various portions of the imaging system 16.An imaging gantry 34 in which is positioned a source unit 36 and adetector 38 may be connected to the mobile cart 30. The gantry may beO-shaped or toroid shaped, wherein the gantry is substantially annularand includes walls that form a volume in which the source unit 36 anddetector 38 may move. The mobile cart 30 can be moved from one operatingtheater to another and the gantry 34 can move relative to the cart 30,as discussed further herein. This allows the imaging system 16 to bemobile and moveable relative to the subject 14 thus allowing it to beused in multiple locations and with multiple procedures withoutrequiring a capital expenditure or space dedicated to a fixed imagingsystem. The control system may include a processor such as a generalpurpose processor or a specific application processor and a memorysystem (e.g. a non-transitory memory such as a spinning disk or solidstate non-volatile memory). For example, the memory system may includeinstructions to be executed by the processor to perform functions anddetermine results, as discussed herein.

The source unit 36 may be an x-ray emitter that can emit x-rays throughthe patient 14 to be detected by the detector 38. As is understood byone skilled in the art, the x-rays emitted by the source 36 can beemitted in a cone and detected by the detector 38. The source/detectorunit 36/38 is generally diametrically opposed within the gantry 34. Thedetector 38 can move in a 360° motion around the patient 14 within thegantry 34 with the source 36 remaining generally 180° opposed (such aswith a fixed inner gantry or moving system) to the detector 38. Also,the gantry 34 can move isometrically relative to the subject 14, whichcan be placed on a patient support or table 15, generally in thedirection of arrow 40 as illustrated in FIG. 1. The gantry 34 can alsotilt relative to the patient 14 illustrated by arrows 42, movelongitudinally along the line 44 relative to a longitudinal axis 14L ofthe patient 14 and the cart 30, can move up and down generally along theline 46 relative to the cart 30 and transversely to the patient 14, toallow for positioning of the source/detector 36/38 relative to thepatient 14. The imaging device 16 can be precisely controlled to movethe source/detector 36/38 relative to the patient 14 to generate preciseimage data of the patient 14. The imaging device 16 can be connectedwith the processor 26 via connection 50 which can include a wired orwireless connection or physical media transfer from the imaging system16 to the processor 26. Thus, image data collected with the imagingsystem 16 can be transferred to the processing system 22 for navigation,display, reconstruction, etc.

The source 36, as discussed herein, may include one or more sources ofx-rays for imaging the subject 14. In various embodiments the source 36may include a single source that may be powered by more than one powersource to generate and/or emit x-rays at different energycharacteristics. Further, more than one x-ray source may be the source36 that may be powered to emit x-rays with differing energycharacteristics at selected times.

According to various embodiments, the imaging system 16 can be used withan un-navigated or navigated procedure. In a navigated procedure, alocalizer and/or digitizer, including either or both of an opticallocalizer 60 and an electromagnetic localizer 62 can be used to generatea field and/or receive and/or send a signal within a navigation domainrelative to the patient 14. The navigated space or navigational domainrelative to the patient 14 can be registered to the image 18.Correlation, as understood in the art, is to allow registration of anavigation space defined within the navigational domain and an imagespace defined by the image 18. A patient tracker or dynamic referenceframe 64 can be connected to the patient 14 to allow for a dynamicregistration and maintenance of registration of the patient 14 to theimage 18.

The patient tracking device or dynamic registration device 64 and aninstrument 66 can then be tracked relative to the patient 14 to allowfor a navigated procedure. The instrument 66 can include a trackingdevice, such as an optical tracking device 68 and/or an electromagnetictracking device 70 to allow for tracking of the instrument 66 witheither or both of the optical localizer 60 or the electromagneticlocalizer 62. The instrument 66 can include a communication line 72 witha navigation/probe interface device 74 such as the electromagneticlocalizer 62 with communication line 76 and/or the optical localizer 60with communication line 78. Using the communication lines 74, 78respectively, the interface 74 can then communicate with the processor26 with a communication line 80. It will be understood that any of thecommunication lines 28, 50, 76, 78, or 80 can be wired, wireless,physical media transmission or movement, or any other appropriatecommunication. Nevertheless, the appropriate communication systems canbe provided with the respective localizers to allow for tracking of theinstrument 66 relative to the patient 14 to allow for illustration of atracked location of the instrument 66 relative to the image 18 forperforming a procedure.

One skilled in the art will understand that the instrument 66 may be anyappropriate instrument, such as a ventricular or vascular stent, spinalimplant, neurological stent or stimulator, ablation device, or the like.The instrument 66 can be an interventional instrument or can include orbe an implantable device. Tracking the instrument 66 allows for viewinga location (including x,y,z position and orientation) of the instrument66 relative to the patient 14 with use of the registered image 18without direct viewing of the instrument 66 within the patient 14.

Further, the gantry 34 can include an optical tracking device 82 or anelectromagnetic tracking device 84 to be tracked with the respectiveoptical localizer 60 or electromagnetic localizer 62. Accordingly, theimaging device 16 can be tracked relative to the patient 14 as can theinstrument 66 to allow for initial registration, automatic registration,or continued registration of the patient 14 relative to the image 18.Registration and navigated procedures are discussed in the aboveincorporated U.S. Pat. No. 8,238,631, incorporated herein by reference.Upon registration and tracking of the instrument 66, an icon 174 may bedisplayed relative to, including superimposed on, the image 18.

Turning reference to FIG. 2, according to various embodiments, thesource 36 can include a single x-ray tube 100 that can be connected to aswitch 102 that can interconnect a first power source A 104 and a secondpower source B 106 with the x-ray tube 100. X-rays can be emitted fromthe x-ray tube 100 generally in a cone shape 108 towards the detector 38and generally in the direction from the source 100 as indicated byarrow, beam arrow, beam or vector 110. The switch 102 can switch betweenthe power source A 104 and the power source B 106 to power the x-raytube 100 at different voltages and/or amperages to emit x-rays atdifferent energy characteristics generally in the direction of thevector 110 towards the detector 38. The vector 110 may be a centralvector or ray within the cone 108 of x-rays. An x-ray beam may beemitted as the cone 108 or other appropriate geometry. The vector 110may include a selected line or axis relevant for further interactionwith the beam, such as with a filter member, as discussed furtherherein.

It will be understood, however, that the switch 102 can also beconnected to a single variable power source that is able to providepower characteristics at different voltages and/or amperages rather thanthe switch 102 that connects to two different power sources A 104 and B106. Also, the switch 102 can be a switch that operates to switch asingle power source between different voltages and amperages. Further,the source 36 may include more than one source that is configured oroperable to emit x-rays at more than one energy characteristic. Theswitch, or selected system, may operate to power the two or more x-raystubes to generate x-rays at selected times.

The patient 14 can be positioned within the x-ray cone 108 to allow foracquiring image data of the patient 14 based upon the emission of x-raysin the direction of vector 110 towards the detector 38.

The two power sources A and B 104, 106 can be provided within the sourcehousing 36 or can be separate from the source 36 and simply be connectedwith the switch 102 via appropriate electric connections such as a firstcable or wire 112 and a second cable or wire 114. The switch 102 canswitch between the power source A 104 and the power source B 106 at anappropriate rate to allow for emission of x-rays at two differentenergies through the patient 14 for various imaging procedures, asdiscussed further herein. The differing energies can be used formaterial separation and/or material enhanced reconstruction or imagingof the patient 14.

The switching rate of the switch 102 can include about 1 millisecond(ms) to about 1 second, further including about 10 ms to 500 ms, andfurther including about 50 ms. According to various embodiments, thepower may be switched at a rate of about 30 Hz. Thus, x-rays may beemitted with energy characteristics according to each power source A andB for about 33 ms.

Further, the power source A 104 and the power source B 106 can beprovided to include different power characteristics, including differentvoltages and different amperages, based upon selected contrastenhancement requirements. The different power characteristics allow thex-rays to include different energy characteristics. The differing energycharacteristics of two or more different x-rays emissions interact andare attenuated (e.g. absorbed, blocked, deflected, etc.) by the samematerial differently. For example, as discussed further herein,different energy characteristics can be selected to allow for contrastenhancement (e.g. enhanced viewing and identification) between softtissue (e.g. muscle or vasculature) and hard tissue (e.g. bone) in thepatient 14, that may be done without any contrast agent present. Also,differing energy characteristics may assist in increasing contrastbetween a contrast agent injected in the patient 14 and an area withouta contrast agent injected in the patient 14.

As discussed further herein, each emission of x-rays at a selectedenergy characteristic may include a x-ray energy spectral range. Thex-ray energy spectral range for any given powering level, however, maybe generally broad. Broad, for example, may include a range of energiesat which x-rays are emitted and not only at a specific and/or singleenergy level. Thus, even if two different powering characteristics areused, emitted x-rays may overlap between two emissions of x-raysgenerated with the two power sources A and B. A filter assembly 200 mayinclude a filter member of a filter material, as discussed herein, whichmay be used to attenuate some of the spectra of one or more of anemission of x-rays. In attenuating part of a spectrum of an emission ofx-rays, differentiation between two emissions may be greater andspectral overlap may be minimized. For example, the filter member mayattenuate lower energy x-rays from when the x-ray tube is powered by thehigher powered power source A or B.

As an example, the power source A 104 can have a voltage of about 75 kVand can have an amperage of about 50 mA, which can differ from the powersource B which can have a voltage of 150 kV and 20 mA. The selectedvoltages and amperages can then be switched with the switch 102 to powerthe x-ray tube 100 to emit the x-rays with selected energycharacteristics generally in the direction of the vector 110 at and/orthrough the patient 14 to the detector 38. It will be understood thatthe range of voltages for the power source A may be about 40 kV to about80 kV and the amperages can be about 10 mA to about 500 mA. Generally,the power characteristic differences between the first power source A104 and the second power source B 106 can be about 40 kV to about 60 kVand about 20 mA to about 150 mA. In other words, for example, the powersource B may power the x-ray tube 100 at a voltage that is about 40 kVto about 60 k V and an amperage that is about 20 mA to about 150 mAgreater than power source A. In addition to the energy and mAdifference, the pulse width of the exposure may be varied as well from 1ms to 50 ms.

The dual power sources allow for dual energy x-rays to be emitted by thex-ray tube 100. As discussed above, the two or dual energy x-rays canallow for enhanced and/or dynamic contrast reconstruction of models ofthe subject 14 based upon the image data acquired of the patient 14. Itis understood, however, that more than two power sources may be providedor they may be altered during operation to provide x-rays at more thantwo energy characteristics. The discussion herein of two or duel energyis merely exemplary and not intended to limit the scope of the presentdisclosure, unless specifically so stated.

Generally, an iterative or algebraic process can be used to reconstructthe model (such as for the image 18) of at least a portion of thepatient 14 based upon the acquired image data. It is understood that themodel may include a three-dimensional (3D) rendering of the imagedportion of the patient 14 based on the image data. The rendering may beformed or generated based on selected techniques, such as thosediscussed herein.

The power sources can power the x-ray tube 100 to generate two dimension(2D) x-ray projections of the patient 14, selected portion of thepatient 14, or any area, region or volume of interest. The 2D x-rayprojections can be reconstructed, as discussed herein, to generateand/or display three-dimensional (3D) volumetric models of the patient14, selected portion of the patient 14, or any area, region or volume ofinterest. As discussed herein, the 2D x-ray projections can be imagedata acquired with the imaging system 16, while the 3D volumetric modelscan be generated or model image data.

For reconstructing or forming the 3D volumetric image, appropriatealgebraic techniques include Expectation maximization (EM), OrderedSubsets EM (OS-EM), Simultaneous Algebraic Reconstruction Technique(SART) and Total Variation Minimization (TVM), as generally understoodby those skilled in the art. The application to perform a 3D volumetricreconstruction based on the 2D projections allows for efficient andcomplete volumetric reconstruction. Generally, an algebraic techniquecan include an iterative process to perform a reconstruction of thepatient 14 for display as the image 18. For example, a pure ortheoretical image data projection, such as those based on or generatedfrom an atlas or stylized model of a “theoretical” patient, can beiteratively changed until the theoretical projection images match theacquired 2D projection image data of the patient 14. Then, the stylizedmodel can be appropriately altered as the 3D volumetric reconstructionmodel of the acquired 2D projection image data of the selected patient14 and can be used in a surgical intervention, such as navigation,diagnosis, or planning. The theoretical model can be associated withtheoretical image data to construct the theoretical model. In this way,the model or the image data 18 can be built based upon image dataacquired of the patient 14 with the imaging device 16.

The 2D projection image data can be acquired by substantially annular or360° orientation movement of the source/detector 36/38 around thepatient 14 due to positioning of the source/detector 36/38 moving aroundthe patient 14 in the optimal movement. An optimal movement may be apredetermined movement of the source/detector 36/38 in a circle alone orwith movement of the gantry 34, as discussed above. An optimal movementmay be one that allows for acquisition of enough image data toreconstruct a select quality of the image 18. This optimal movement mayallow for minimizing or attempting to minimize exposure of the patient14 and/or the user 12 to x-rays by moving the source/detector 36/38along a path to acquire a selected amount of image data without more orsubstantially more x-ray exposure.

Also, due to movements of the gantry 34, the detector need never move ina pure circle, but rather can move in a spiral helix, or other rotarymovement about or relative to the patient 14. Also, the path can besubstantially non-symmetrical and/or non-linear based on movements ofthe imaging system 16, including the gantry 34 and the detector 38together. In other words, the path need not be continuous in that thedetector 38 and the gantry 34 can stop, move back the direction fromwhich it just came (e.g. oscillate), etc. in following the optimal path.Thus, the detector 38 need never travel a full 360° around the patient14 as the gantry 34 may tilt or otherwise move and the detector 38 maystop and move back in the direction it has already passed.

In acquiring image data at the detector 38, the dual energy x-raysgenerally interact with a tissue and/or a contrast agent in the patient14 differently based upon the characteristics of the tissue or thecontrast agent in the patient 14 and the energies of the two x-raysemitted by the x-ray tube 100. For example, the soft tissue of thepatient 14 can absorb or scatter x-rays having an energy produced by thepower source A 104 differently than the x-rays having energy produced bythe power source B 106. Similarly, a contrast agent, such as iodine, canabsorb or scatter the x-rays generated by the power source A 104differently from those generated by the power source B 106. Switchingbetween the power source A 104 and the power source B 106 can allow fordetermination of different types of material properties (e.g. hard orsoft anatomy or between two types of soft anatomy (e.g. vessels andsurrounding tissue)), contrast agent, implants (e.g. metal implants) andsurrounding natural anatomy (e.g. bone), or etc. within the patient 14.By switching between the two power sources 104, 106 and knowing the timewhen the power source A 104 is used to generate the x-rays as opposed tothe power source B 106 to generate the x-rays the information detectedat the detector 38 can be used to identify or segregate the differenttypes of anatomy or contrast agent being imaged.

A timer can be used to determine the time when the first power source A104 is being used and when the second power source B 106 is being used.This can allow the images to be indexed and separated for generatingdifferent models of the patient 14. Also, as discussed herein, thetimer, which can be a separate system or included with the imagingsystem 16 or the processor system 26, can be used to index image datagenerated with the contrast agent injected into the patient 14.

At least because the x-ray tube 100 is in a moveable imaging system,such as the imaging system 16, it can be moved relative to the patient14. Thus, the x-ray tube 100 may move relative to the patient 14 whilethe energy for the x-ray tube 100 is being switched between the powersource A 104 and the power source B 106. Accordingly, an image acquiredwith the power source A 104 may not be at the same pose or positionrelative to the patient 14 as the power source B 106. If the model isdesired or selected to be formed of a single location in the patient 14,however, various interpolation techniques can be used to generate themodel. Interpolation may between image data acquired at a first time andimage data acquired at a second time. The image data at the first andsecond times may be generated with the two different energies. Thus, themodel may be formed including image data from both energies usinginterpolation between the acquired image data. Further, theinterpolation may be to account for an amount of movement (e.g. linear,rotational, etc.) of the x-ray tube 100 between when the projection withthe power source A 104 and the projection with the power source B 106was acquired.

The dual energy of the x-rays emitted by the x-ray tube 100 due to thetwo power sources 104, 106 can allow for substantially efficient andenhanced contrast discrimination determination between the vasculatureand the musculature of the patient 14. Moreover, the switching by aswitch 102 between the power source A 104 and the power source B 106allows for an efficient construction of the source 36 where the singlex-ray tube 100 can allow for the generation of x-rays at two differentenergies to allow for enhanced or dynamic contrast modeling of thepatient 14, such as modeling the vasculature of the patient 14 includinga contrast agent therein.

The patient 14 can also be imaged with the injected contrast agent bygating the acquisition of the image data of the patient 14 based uponthe injection of the contrast agent. According to various embodiments, acontrast agent, such as iodine, can be injected into the patient 14 toprovide additional contrast in the image data acquired of the patient 14with the imaging system 16. During the image acquisition, however, thecontrast agent flows through the vasculature of the patient 14 from anartery phase to a venous phase. For example, the contrast agent can beinjected into the patient 14 into an artery where the contrast agent canflow through the vasculature of the patient 14 to the heart, through theheart, to the lungs through the venous system, back through the heart,and out into the arterial portion of the vasculature of the patient 14.

When acquiring image data of the patient 14 to identify or reconstructthe vasculature of the patient 14, knowing the timing of when image datais acquired relative to the timing of the injection of the contrastagent can allow for a reconstruction of the various phases based on theknown movement of the contrast agent through structures of the patient14. In other words, it is generally understood that the contrast agentwill flow through the patient 14 as described above at a known orgenerally known rate. The dual energy x-rays, generated with the x-raytube 100 based upon the power source A 104 and the power source B 106,can be used to generate image data of any portion of the vasculature ofthe patient 14.

The acquisition of the image data, therefore, can be gated relative tothe injection of the contrast agent into the patient 14. For example,the controls 32 of the imaging system 16 can be associated orcommunicate with a control of a pump 170 (illustrated in FIG. 1) througha communication line 172 (illustrated in FIG. 1) that pumps or injectsthe contrast agent into the patient 14. The communication 172 betweenthe pump 170 and the imaging device control 32 can be any appropriatecommunication such as a wired, wireless, or other data communicationsystem. Also, the control for the pump 170 can be incorporated into thecontrols 32 of the imaging system 16 or the processor system 26.

Duel energy imaging systems may include those disclosed in U.S. Pat.App. Pub. Nos. 2012/0099768 and 2012/0097178, both incorporated hereinby reference.

In addition to the generation of x-rays of different energies, includingdual energy x-rays as discussed above, the filter assembly 200 can beused to assist in insuring or creating a select differentiation betweenx-ray spectras of x-rays of the two different energies. The filterassembly 200 can also be timed in conjunction with the pump 170 and theacquisition of the image data to assist in gating image data acquired ofthe patient 14. Therefore the filter assembly 200 can be operated toimage the patient 14 to achieve the differentiation between the dualenergies of the x-rays.

Turning reference to FIG. 3 a filter assembly 200 a is illustrated. Thefilter assembly 200 a may be provided in the imaging system 16 such thatthe x-rays emitted from the x-ray tube will selectively pass through afilter member 210 of the filter assembly 200 a. The filter assembly 200a may include a motor assembly 220. The motor assembly 220 may be anyappropriate motor assembly that is assembled into the imaging system 16while not interfering with operation of the imaging system 16. Exemplarymotor assemblies include various stepper and/or brushless servo motors,such as the Maxon® EC-max 30 DC brushless motor sold by Maxon Motor Ag,having a place of business in Switzerland.

Generally the motor assembly 220 may be a motor assembly to rotationallydrive an axle or shaft 224. Mounted to the shaft 224 may be a filtermember holding member 226. The holding member 226 may be fixed to theaxle 224 with a set screw in a bore 228. The shaft 224 may be receivedwithin a bore 230 of an shaft connection portion 232 of the holdingassembly 226. Extending from the shaft mounting portion 232 may be afilter holding portion 236. The filter member 210 may be positioned onthe holding portion 236 in a selected manner. For example, the filterportion 210 may be mounted with a fixative material, such as anadhesive, or with a mounting hardware, such as rivets or bolts.According to various embodiments the filter member 210 may be a metallicmaterial that is brazed or welded to the holding portion 236. Theholding portion may be formed as a frame, such that x-rays passingthrough the subject will pass only through the filter member 210 and nota portion of the holding portion 236.

The motor assembly 220 may be driven or controlled with a controllerthat is internal to the motor assembly 220. Further, the motor assembly220 may be controlled with the imaging controller 32. The imaging systemcontroller 32 may control the imaging system 16 including the filterassembly 200 a to image the patient 14 according to a selected imagingmodality. The filter assembly 200 a may be driven or operated to assistin acquiring dual energy image data of the patient 14, as discussedfurther herein. The imaging sensing controller 32 may control themovement and position of the source 36 and the operation of the filterassembly 200 a. As discussed above, the controller 32 may include amemory with a predetermined imaging protocol (including timing ofimaging, number of image projections, etc.) and a related timing foroperating the motor assembly 220 to move the filter.

The motor assembly 220 may include a motor assembly that is able torotate the filter member 210 or the filter holding portion 236substantially in either or both directions of double headed arrow 240 ata selected velocity and stopping the filter member 210 at a selectedtime. Generally, the motor assembly 220 may operate to move the filtermember 210 in a first direction and then stop and move the filter memberin a second, such as opposite, direction. For example, during operationthe filter member 210 may move generally 90° into and out of the beam ofx-rays, such as along vector 110. As discussed above, the x-ray beam mayswitch energy characteristics depending upon which power source A or B104, 106 is powering the x-ray tube 100. The rate of switching may beabout 30 Hz. Therefore, the filter member 210 may need to accelerate atabout 900,000 degrees/s² to move into the beam path 110 so that thefilter member 210 is appropriately positioned in about 23 milliseconds.

As schematically illustrated in FIG. 3, the x-ray tube 100 may emit tothe x-rays generally in the direction of the vector 110. The x-rays willthen impinge and pass through or be blocked by the filter member 210 tobe filtered before reaching the patient 14 and the detector 38. When thefilter 210 is selected to be filtering the x-rays from the x-ray tube100, the filter member 210 may be moved in a first direction andpositioned as illustrated in FIG. 3 such that the filter member 210 isin a first position in the path of the x-rays along ray 110. The filtermember 210 may then be moved in a second direction and positioned in asecond position as illustrated in phantom at 236′ in FIG. 3 that is outof the x-rays path and not in the ray 110. The movement from the firstposition to the second position by the filter member 210 may besubstantially 90° as illustrated between the carrier 236 and the carrier236′, shown in phantom.

The motor assembly 220 may, therefore, be any appropriate motor that isable to move at a selected speed. The selected speed may include timefor moving the carrier 236 and emitting x-rays for acquiring image data.In various embodiments, therefore, a selected speed may include about4500 RPM so as to move the carrier or filter holding portion 236 at aspeed of about 90° about every 20 milliseconds (ms). This would allowthe filter 210 to move into and out of the x-beam 110 about every 33 msand allow about 10 ms to about 13 ms to be allocated for acquiring theimage data with the x-ray beam 110. Appropriate motors may include DCservo motors, AC servo motors, stepper motors, or other appropriatemotors. The motor assembly 220 may include direct drive or gearedassemblies. As illustrated in FIG. 3 the shaft 224 may extend directlyfrom the motor and engage directly in the filter holding portion 226. Itis understood that the motor assembly 220, however, may also be providedto operate or move the filter holding portion 236 via a transmission orother appropriate non-direct drive system.

One or more encoders may be provided in the motor assembly 220 todetermine a position of the motor including the shaft 224. For example,an encoder 242 may attach to the shaft 224 and a housing 243 of themotor assembly 220 and/or be incorporated into the motor assembly 220.The encoder 242 may include incremental or absolute encoders that may beoptical, magnetic, or inductive. The encoder 242 may track or determinethat the position of the shaft 224 and, therefore, the filter holdingportion 226 fixedly attached to the shaft 224. For example, the encoder242 may include a reader or a sensor at both the “in” position and “out”of beam position (illustrated in phantom 236′). The encoder 242 may thenprovide a signal to the controller 32 regarding the sensed location. Theencoder 242 may then provide the position of the filter holding portion226 to the image controller 32. The image controller 32 may operate themotor assembly 220 appropriately to move the filter member 210 into orout of the path 110 of the x-rays from the x-ray tube 100 based on thetiming of the emission of x-rays at the selected energy and the positionof the filter member 210. Thus, the movement of the filter member 210may be timed and selected based on the timing and/or emission signal ofthe x-rays at the selected first or second energy.

Accordingly, during an operation the two power sources A and B 104, 106may selectively and alternatively power the x-ray tube 100. During aselected operation, such as powering the x-ray tube with the powersource B 106 the filter member 210 may be positioned in the path 110 ofthe x-rays in the first position. As the imaging control system 32 isable to determine and power the x-ray tube 100 with the power source B104 the control system 32 may also operate the filter assembly 200 a tomove the filter member 210 into the path when powering the x-ray tube100 with the set power source B 104. The encoder 242 may be used todetermine that the filter member 210 is in the appropriate positionrelative to the path of the x-rays 110 to ensure the filter 210 ispositioned for acquiring image data of the patient 14. When the powersource A is powered to emit x-rays along ray 110, the filter member 210may be moved by the motor assembly 220 to the second position (shown inphantom 236′ in FIG. 3) out of the path of the x-rays along ray 110.

It is understood, however, that the filter holder may continuously spinon the shaft 224 in a single direction, such as in a rotation of atleast 360°. The encoder 242 may then provide a signal as to when thefilter member is in the in-beam position, as illustrated in solid linesin FIG. 3. The movement of the filter member 210 and the carrier 236 maythen be synchronized to the emission of x-rays at a selected energyparameter with one of the selected power sources A, B 104, 106.Synchronization may occur, as discussed herein.

Moreover, it is understood that the filter carrier portion 226 mayinclude more than one filter carrier portion 236 with more than one ofthe filter members 210. For example, two filter members may be providedsubstantially 180 degrees from each other. Such that at one speed ofrotation, a filter will be in the beam path 110 twice as often. Further,any appropriate number of filter members may be provided.

As discussed above the filter material may be selected to selectivelyeliminate a certain portion of an x-ray spectra. As the x-rays from thex-ray tube 100 may be powered with the power source B 104 the x-rays,however, may still include a spectra that is greater than selected.Accordingly, the filter member 210 may filter the x-rays with the secondenergy to include a spectra that is narrower or has a higher or lowermean energy than may be provided by only powering the x-ray tube 100with the power source B 106. Further, the filter material 210 may beselected to achieve a selected x-ray spectra, such that its averageenergy if approximates 60-80 kV different than its unfiltered spectrum.Accordingly, selected filter materials may include copper, aluminum, orother high-z materials. It is also understood, however, that the filtermember 210 may be used to filter x-rays powered at the power source A104. Furthermore, the filter member 210 may be used to filter x-rayspowered with both power sources A and B 104, 106. And further, more thanone filter member may be provided such that a first filter member willfilter x-rays powered with the power source A 104 and a second filterwill filter x-rays with the power source B 106.

Turning reference to FIG. 4, a filter assembly 200 b is illustrated. Thefilter assembly 200 b may be incorporated into the imaging system 16either with or alternative to the filter assembly 200 a, discussedabove. The filter assembly 200 b may include a filter member or portion260 that may be moved substantially linearly generally in two directionsin a plane, such as a plane defined by the filter member 260 and/orparallel thereto, in the direction of double headed arrow 262. Thefilter assembly 200 b may be positioned so that the filter member 260may be moved in a first direction to a first position to intersect thebeam of x-rays along vector 110 emitted from the x-ray tube 100, asschematically illustrated in FIG. 4. The filter member 260 on the filtercarrier 264 may then be moved in a second, such as an opposite ordifferent direction, to a second position such that the filter member260 is out of the x-ray path along vector 110. The filter member 260 maybe carried on a filter carrier 264 that is driven by a linear motor oractuator 270.

The linear motor 270 may include a linear motor according to variousembodiments. For example, the linear motor 270 may include appropriatelinear motors that include moveable or fixed magnets and moveable orfixed motor coils. Exemplary linear motors include slotless linearmotors, balanced linear motors, etc. Exemplary commercially availablelinear motors include the Javelin™ Series Motors including models 1486and 1487 and/or the flatbody Juke™ Series Motors sold by Celera Motionhaving a place of business in Loomis, Calif. The linear motor 270 maymove the filter carrier 264 in the plane relative to the ray 110 of thex-rays at a selected rate and/or at a selected time. As discussed above,x-rays at the different energy characteristics may be emitted from thex-ray tube 100 at a frequency of about 30 Hz. Therefore the filtermember 260 generally would need to move into the ray 110 within about 23milliseconds to allow for an exposure of about 10 milliseconds of thepatient 14 to the x-ray. Thus, the filter member 260 may be timed tomove into and out of the x-ray beam to affect only the selected beam ofx-rays at a selected energy characteristic, such as to have the effectof eliminating a portion of the emitted x-ray spectra.

According to various embodiments, the linear motor 270 may include astationary linear motor coil 274 and a moving magnet 276. The stationarycoil 274 may be fixed to a structure, such as a base plate or member 278and/or one or more linear bearings 280. The moving magnet 276 positionedover the or relative to the stationary linear motor coil 274 may movegenerally in the direction of the double headed arrow 262. The filtercarrier 264 may be mounted to the moving magnet 276 using an appropriatemechanism, such as an adhesive, screws, rivets, or the like. Forexample, one or more bores 282 may be provide in the filter carrier 264to allow for a fixation member, such as a screw, to fix the filtercarrier 264 to the moving magnet 276.

In operation, the moving magnet 276 may be driven in the directions ofarrow 262 by the stationary motor coil 274. The operation of the linearmotor in such a configuration is generally understood by one skilled inthe art, and will not be described herein in detail. Nevertheless, thestationary motor coil 274 may be operated to sequentially power coilswithin the stationary motor coil 274 to move the moveable magnet 276 viamagnetic field interactions with the moveable magnet 276. The moveablemagnet 276 may include permanent and/or electromagnets that interactwith coils in the stationary coil 274 to move the moveable magnet 276.As the filter carrier 264 is fixed to moveable magnet 276, the filtercarrier 264 carrying the filter 260 may move with the moveable magnet276. The linear bearings 280 may hold and guide the filter carrier 264connected to the moveable magnet 276 in a selected manner. The linearbearings 280 may ensure that the filter carrier 264 and the moveablemagnet 276 move generally in the direction of arrow 262.

The driving motor coil 274 may be connected to the image controller 32to operate the motor 270 according to a predetermined timing or gatingof positioning the filter 260 in the x-rays. As discussed above inrelation to the filter assembly 200 a, the image controller 32 controlsand determines the timing of imaging with the x-rays. The imagecontroller 32 includes a predetermined timing for powering x-rays atselected energies to acquire image data of the patient 14. Therefore,the image controller 32 may control the linear motor 270 to move thefilter member 260 into and out of the vector 110 of x-rays from thex-ray tube 100 according to a determined or predetermined x-ray imagingplan. As discussed above, the controller 32 may include a memory with apredetermined imaging protocol (including timing of imaging, number ofimage projections, etc.) and a related timing for operating the motorassembly 270 to move the filter.

For example, the imaging controller 32 may include a selecting timeand/or frequency of emitting x-rays powered by either or both of thepower source A 104 and the power source B 106. The movement of thefilter member 260 into the x-ray beam along vector 110 may be selectedand timed relative to the emission of x-rays. The movement of the filtermember 260 with the linear motor 270 may be synchronized to the emissionof the x-rays. In various embodiments, the movement of the filter 260with the linear motor 270 controlled by the controller 32 may be cyclicaccording to a predetermined cycle or may be infrequent according to aselected imaging protocol. Nevertheless, the controller 32 may controlthe motor 270 to move the filter member 260 in the direction of thedouble headed arrow 262 to position the filter member 260 in the ray 110of the x-rays or to move it out of the way.

The position of the motor 270 may be determined with an encoder, such asa linear encoder 290. The linear encoder 290 may include an inductiveencoder having a fixed read head 292 and a rail 294 connected to andmoveable with the filter carrier 264. It is understood, however, thatthis may be vice-versa so that the read head 292 moves with the moveablewith the filter carrier 264 while the rail 294 is fixed relativethereto. Nevertheless, the read head 292 may also be connected to thecontroller 32 so that the read head 292 is operable to transmit a signal(e.g. a position signal) to the controller 32 regarding a position ofthe filter carrier 264. Based on the signal, the controller 32 maydetermine an absolute or an incremental position of the filter carrier264. The controller 32 may therefore determine the position of thefilter member 260 by determining a position of the filter carrier 264via the encoder 290. It is understood, however, that the encoder 290 maybe any appropriate encoder such as an optical encoder, rotary encoder,or alternative linear encoder. Further, optical and magnetic technologymay be used as an alternative or in addition to an inductive encoder.

Moving the filter member 260 in a linear manner via an appropriatefilter carrier 264 may also be performed with other linear motors suchas a lead screw or ball screw, a balanced linear motor, a worm screw, orother appropriate drive mechanism. Further, it will be understood that alinear motor, according to various embodiments, may include the drivecoil 274 which moves and the magnet 276 that is fixed. In a moving coilassembly, the filter carrier 264 may be mounted on the drive coil 274and the magnetic 276 be fixed to a mounting portion such as the mountingplate 278 or the bearings 280.

With reference to FIG. 5 a filter assembly 200 c is illustrated. Thefilter assembly 200 c may include a filter member 300 that is carried bya filter carrier 310, wherein the filter carrier 310 may rotate aroundan axis on a shaft. The filter member 300 may be formed of a selectedmaterial, including those discussed above, and fixed to the filtercarrier 310. For example, bores may be formed in the filter member 300and one or more screws 312 fix the filter member 300 to the filtercarrier 310 by passing through or engaging the filter member 300 and thefilter carrier 310. It is understood that other fixation mechanisms maybe provided, such as welding, adhesives, brazing, or the like, to fixthe filter member 300 to the filter carrier 310. The carrier 310 mayfurther be provided as a frame such that x-rays that pass through thefilter member 300 and reach the detector pass through the filter member300, but not the material of the filter carrier 310.

As illustrated in FIG. 5 the filter carrier 310 may have a curved outeredge 314 such that the filter carrier 310 includes a radius 316 and hasan outer arcuate edge 314. The filter carrier 310, therefore, may format least a part of a circle or round member. The combination of thefilter carrier 310 and the filter member 300 may have a selected massthat defines or forms only a portion of a circle. Therefore, acounterbalance 320 may be fixed to the filter carrier 310 to counterbalance the mass of the filter member 300 and the filter carrier 310.

The counter balance may have an arcuate outer edge 322 and asubstantially similar radius 324 to the radius 316. The counter balance320, therefore, may form with the filter carrier 310 a circle. Thecounterbalance 320 and the filter carrier 310 form a filter carrierassembly 350 to move the filter member 300 relative to the x-ray to bepositioned into or out of the x-rays generally travelling along thedirection 110, as schematically illustrated in FIG. 5.

The filter carrier 310 may rotate around a shaft that has or forms acentral axis 330. The filter carrier 310 may be operated to rotate intwo directions or in a single direction, such as in the direction ofarrow 340 around the axis 330. In various embodiments, the filtercarrier 310 may be moved to carry the filter member 300 in substantiallyone rotational directional.

According to various embodiments the filter carrier 310 may be operatedto rotate around the axis 330 at a substantially constant speed androtation per minute (RPM). Therefore, whether the filter member 300 isin the beam path 110 or an open area of the filter carrier assembly 350in the beam path 110. As the filter carrier 310 rotates around the axis330 in the direction of arrow 340 in open air or void region 344, formedat least in part by the counter balance 320, may also be spaced orpositioned in the beam path 110. Therefore, the rotation of the filtercarrier 310 around the axis 330 can alternately place the filter member300 in the beam path 110 or the void 344 in the beam path 110. It isunderstood, however, that the filter member 300 may have a size andmoving the filter member 300 cause a void to be in the beam path, thusforming a void with a counter balance 320 is not required.

The filter carrier 310 on the assembly may need to rotate, such in thedirection of arrow 340, at a selected rate to ensure that the filtermember 300 is in the beam path 110 at a selected time. In this manner,the imaging with a filter and without a filter may be gated andcontrolled by the controller 32. Gating may be based upon various and/orpredetermined factors such as energy selection of the x-rays, contrastagent injection, patient physiological motion (e.g. respiration or heartbeat). As discussed above the filter member 300 may be positioned in aselected position in the beam path 110 to filter a selected portion ofx-ray spectra of at least one of the emissions of x-rays at one of theenergies of the dual x-ray imaging system at a selected time. Asdiscussed above, it may be selected to switch the energies forgenerating x-rays of the imaging system at a frequency of about 30 Hz.Therefore, moving the filter member into and out of the beam may occurat about 33 milliseconds.

As illustrated in FIG. 5, the filter member 300 may be on one side ofthe filter carrier assembly 350 and may form about one-half of thecircumference of a disk, therefore a one-half revolution of the filtercarrier assembly 350 may be required to ensure movement of the filtermember 300 into a first position in the x-ray beam along the vector 110and movement to a second position that is out of the beam of the x-raysalong the vector 110. Therefore, approximately 900 rotations per minutemay be selected to achieve movement into and out of the beam at a rateto match the switching of the x-ray tube 100.

With continuing reference to FIG. 5 and additional reference to FIG. 6,the filter carrier assembly 350 may be connected to a carry gear 360,where the filter carrier assembly 350 is removed in FIG. 6 for clarityof the following discussion. The carry gear 360, in various embodiments,is driven by a belt 364 that is driven by a drive gear 366 that isconnected to a shaft 370 powered by a motor assembly 374. The motorassembly 374 may include a housing 376 and a powered motor (notspecifically illustrated) within the housing 376. The motor assembly 374may be powered by various power mechanisms, such as electrical power,pneumatic power, or the like. The motor assembly 374 may be anyappropriate motor assembly that can drive the filter carrier assembly350 at the selected speed and be powered by the imaging system 16 andcontrolled by the controller 32. The motor assembly 374 may include anappropriate stepper and/or servo motors, for example the Maxon® EC-I-40brushless DC servo motor sold by Maxon Motor Ag having a place ofbusiness in Switzerland.

Control connection 380 may be provided and interconnected with theimaging system controller 32. As discussed above, the positioning of thefilter member 300 may be controlled by the imaging system controller 32to filter x-ray spectra, as discussed above. The filter member carrierassembly 350 may be mounted to the carry gear 360 through theappropriate mechanism, such as one or more screws, bolts, adhesives,rivets, or other appropriate mechanical or chemical adhesions of thecarrier assembly 350 to the carry gear 360. Therefore, upon rotation ofthe drive gear 366 the belt 364 may drive the carry gear 366 to spin thefilter carrier assembly 350, including the filter member 300, at aselected rotation rate. It is understood, however, that the motorassembly 374 may be directly connected to the carry gear 360 withoutrequiring the belt 364. In a direct connection, for example, the carrygear 360 may be mounted directly to the shaft 370 (e.g. replacing thedrive gear 366) and/or the carry gear 360 may directly engage the drivegear 366 without the belt 364 and/or other transmission system.Alternatively, other appropriate drive or transmission mechanisms may beprovided between the drive gear 366 and the carry gear 360 such as aworm drive, a geared transmission, or other appropriate connectionsystems.

During operation, the position of the filter member 300 may be syncedwith the location of the beam 110 in time with the emission of thex-rays at the selected power that are intended or selected to passthrough the filter member 300 before reaching the patient 14. Accordingto various embodiments the filter assembly 200 c may include an encoderassembly 388. The encoder assembly 388 may include a magnetic encoderthat may include a sensing magnet portion 390 and a transmittingmagnetic portion 392. The encoder assembly 388 may be positioned near orat the carrying gear 360 such that it is positioned at the location ofthe filter member 300. For example, the sending magnet portion 392 canbe positioned at a location that is adjacent or near the filter member300. Therefore, when the magnetic portion 392 passes the reading portion390 an index signal may be transmitted that the filter member 300 is thelocation of the beam 110.

The encoder assembly 388 may additionally and/or alternatively include amagnetic encoder such as the RMB20 magnetic encoder module and magnetsold by Renishaw having a place of business in West Dundee, Ill., U.S.A.In such a system the magnetic encoder 388 may include a magnet 391 thatis incorporated into or in place of an axle to which the magnet 390 maybe otherwise connected. The magnet 391 may rotate with the carrier gear360 as the filter member 300 rotates. As the magnet 391 rotates amagnetic field produced by the magnet 391 moves relative to anintegrated circuit encoder assembly that may be included on anintegrated circuit or printed circuit board assembly system 393 that isfixed relative to the carrier gear 360 and the magnet 391. As isunderstood by one skilled in the art, the integrated circuit system 393can sense the moving magnetic field of the magnet 391 to determine theindex signal as discussed herein. Therefore, the encoder assembly 393may act as the sending portion 392 or alternatively thereto.Accordingly, it is understood by one skilled in the art that the encoderassembly 388 may be provided in any appropriate format including themagnet 391 and encoder assembly 393 as a noncontact magnetic encoder.

During operation, the filter assembly 200 c may be operated orcontrolled such that the movement of the filter carrying member 310 isconstant and synced in time to the emission of the selected x-rays alongthe x-ray beam 110. Direct control of the motor assembly 374 with theimage controller 32 can ensure that the filter member 300 is positionedin the beam of the selected time to filter the x-rays emitted from thex-ray tube 100.

In an alternative and/or additional synchronizing method, the motorassembly 374 may be powered to turn the filter carrier assembly 350 at anominal speed such that the filter carrier assembly 350 may rotate atabout 900 RPMs, as discussed above. In various embodiments, a gear ratiobetween the motor assembly 374 and the carrier gear 360 is 3:1, thus themotor may rotate at about 2700 RPMs to cause rotation of the filtercarrier assembly at about 900 RPMs.

The encoder assembly 388 can be positioned and incorporated such that asingle pulse signal is provided as the carrier assembly 350 rotates onthe carrier gear 360. The index impulse may be aligned with the positionof the beam 110 in the imaging system 16. Therefore, an indication orsignal of when the filter member 300 is positioned in the beam 110 maybe determined based upon an index pulse. To ensure that the filtermember 300 is positioned at the beam 110 at the selected time, asynchronization process 400, as illustrated in FIG. 7, may occur once atstart-up of the imaging system 16 or at a selected rate during imagingto ensure constant synchronization. As discussed above, the controller32 may include a memory with a predetermined imaging protocol (includingtiming of imaging, number of image projections, etc.) and a relatedtiming for operating the motor assembly 370 to move the filter carrierassembly 350. Further, the synchronization process 400 may be encoded asinstructions to be recalled from the memory and executed by theprocessor.

Initially, the motor may be started in block 402 to initiate rotation ofthe filter carrier assembly 350 at the selected constant speed, such asabout 900 RPMs. After starting the motor and rotating the filter carrierassembly 350, an in-position or index pulse can be received by thecontroller 32 in block 404. The in-position or index pulse, as notedabove, can occur as the sending portion 392 passes the receiver portion390 at the location of the beam 110, thus signaling that the filtermember 300 is in position relative to the beam 110 and would filterx-rays, if x-rays were being emitted. The signal from block 404 can thenbe compared with a selected x-ray exposure signal in block 408. As notedabove, the x-ray exposure may switch between at least two energies in adual energy system at a selected rate, such as about 30 Hz. Therefore,the in-position signal when the filter member 300 is in positionrelative to the x-ray beam 110 can be compared to the appropriate timingor frequency of the selected x-ray emission.

A decision block of “in sync” 410 can be used to determine whether thefilter member 300 is in sync with the selected x-ray emission timing andsignal by the comparison in block 408. If it is determined in block 410that the filter member 300 is in sync, then a YES path 420 may be passedto end the synchronization procedure in END block 426. The speed of themovement, including rotation, of the filer carrier assembly 350 may notchange, therefore. Following the ending of the synchronization procedure400, imaging may occur according to the selected imaging procedure, suchas controlled by the controller 32, at the selected constant speed.

If synchronization is determined to not have occurred, a NOT path 440may be followed to a synchronization procedure 446. The synchronizationprocedure 446 may include various steps such as determining a positionoffset in block 450. After determining a position offset, a send commandto change velocity in block 456 may be made. The send command to changevelocity in block 456 may be sent by the imaging system controller 32.

The send command to change velocity may increase or otherwise change thevelocity of the carrier assembly 350 from the selected constant speed.For example, the speed may be increased from 900 RPMs to about 1000RPMs, or about 2000 RPMs, or any selected speed. The velocity change maybe for a selected period of time to correct for the position offset toachieve alignment or synchronization of the phase of the position of thefilter member 300 with the timing of the emission of the x-rays. Forexample, the speed of the motor assembly 374 may be increased by aselected amount to position the filter member 300 within the x-ray beam110 at the timing signal or emission signal for the x-rays at theappropriate time.

After a selected period of time, such as included in the send command tochange velocity command block 456, the velocity of the filter carrierassembly 350 may be returned to the selected constant velocity, such asabout 900 RPMs. The method may then return to block 404 and an inposition signal may again be received from block 404. A comparison tothe emission timing signal in block 408 may then occur. Thus, the insync determination of block 410 can be determined. If it is determinedthat the carrier assembly 350 remains out of sync, the NO path 440 canbe again used to attempt to achieve synchronization in block 446.However, if synchronization is determined, YES path 420 can be followedto the end block 426 and the constant speed may be maintained. Thus, thesynchronization process 400 may be used in a loop to achievesynchronization of the position of the filter member 300 in the beam 110at the time of emission of x-rays.

Accordingly, the motor assembly 374 may be operated to achievesynchronized rotation of the carrier assembly 350 with timing of thex-ray emission without rigid and direct continuous control of the motorassembly via a controller, including the image controller 32. The motorassembly 374 may, therefore, be operated to position the filter member300 and beam 110 at an appropriate time using a synchronizationtechnique, including the synchronization method 400 discussed above, androtating the filter carrier assembly 350 at a constant rate.

Turning reference to FIG. 8, a filter assembly 200 d may include afilter carrier assembly 460. The filter carrier assembly 460 may besimilar to the filter carrier assembly 350 of the filter assembly 200 cillustrated in FIG. 5. Thus, the filter carrier assembly 460 may includea generally circular member having an outer curved edge 464. The filtercarrier assembly 460 may differ, however, by having a first void 468substantially opposed to a second void 472 at about 180° from each otheraround an axis of rotation 480. The filter carrier assembly 460 may alsoinclude two filter members including a first filter member 500 and asecond filter member 504. Each of the filter members may be positionedabout 180° apart around the axis of rotation 480. Further, the voids 468and 472 may be positioned at generally 90° offset from the filtermembers 500 and 504 around the axis of rotation 480. The axis ofrotation 480 may be similar to the axis of rotation 330, as discussedabove and illustrated in FIG. 5, as the carrier assembly 460 may bemounted on the carrier gear 360 of the drive assembly illustrated inFIG. 6. Accordingly, the filter carrier assembly 460 may replace thefilter carrier assembly 350 discussed above.

Accordingly, the filter carrier assembly 460 may alternatively include afilter member and a void at 90° around the axis of rotation 480. Theoperation of the filter carrier assembly 460 may be similar to thefilter carrier assembly 350, as discussed above. However, thepositioning of two filter members about 180° from another may allow therotational speed of the filter carrier assembly 460 to be about one halfthat of filter carrier assembly 350. Accordingly the rotational speed ofthe filter carrier assembly 460 may be about 450 RPMs rather than about900 RPMs. As one skilled in the art will understand, the filter member500 or 504 would be positioned in the beam line 110 at about twice therate as a single filter member, such as a single filter member 300.Therefore the filter member assembly 460 may rotate at substantiallyhalf the speed of the filter member assembly 350.

However, the speed or frequency of operation of the filter carrierassemblies 350 or 460 may be substantially constant during operationonce a selected speed is reached. Therefore, as the carrier assemblies350, 460 achieve the appropriate operational speed the speed may bemaintained and the filter members will be positioned into and out of thebeam 110 at an appropriate time.

Further, the synchronization of the filter carrier assembly 460 mayoccur in a manner similar to that discussed above, such as by thesynchronization method 400. An index signal may be received when one ofthe filter members 500, 504 is within or at an in position thatintersects the beam vector 110. The position of the other filter memberis substantially 180° from the indexed filter member, therefore, thesynchronization will be achieved as the slower speed of the filtercarrier 460 ensures that the opposite filter member will reach the beam110 at the appropriate time even if synchronization is made relative toonly one of the filter members. Therefore, the filter carrier assembly460 may be operated at a speed of substantially half that of the filtercarrier assembly 350, while synchronization and a constant speed maystill be performed and maintained in the manner similar to thatdescribed above.

Accordingly, according to various embodiments, a filter member may bepositioned in the x-ray beam 110 to assist in achieving a selectedspectra to reach the patient 14. Operation of the imaging system 16,therefore, may be used to achieve contrast enhancement of selectedtissues or materials, such as two different soft tissues, hard tissueand soft tissue, contrast agent and other materials, metal and bone, orother selected differing materials. The filter member may be positionedinto and out of the x-ray beam 110 according to various mechanisms,including those discussed above, to achieve further separation of thex-ray spectra at the differing energies.

It will also be understood that the image data and/or model can be usedto plan or confirm a result of a procedure without requiring or usingnavigation and tracking. The image data can be acquired to assist in aprocedure, such as an implant placement. Also, the image data can beused to identify blockages in the vasculature of the patient 14, such aswith the contrast agent. Thus, navigation and tracking are not requiredto use the image data in a procedure.

According to various embodiments, as discussed above, a filter assemblymay be included in a collimator 198 that may be positioned between thex-ray source 100 and the subject 14. As schematically illustrated inFIG. 2, and discussed above, the collimator 198 may include variousfeatures and portions, such as the filter 200, according to variousembodiments, as discussed above. With additional reference to FIG. 9,the collimator 198 may include filters, as discussed above, and variousother portions or systems in addition to the filters, according tovarious embodiments.

As illustrated in FIG. 9, the collimator 198 may also include varioussystems or features to selectively allow x-rays to pass through anexposure opening 600 of the collimator 198. The exposure opening 600 maybe formed as a passage through an exposure ring or exposure member 604.The exposure ring 604 may be formed of a selected material, such amaterial that is opaque to x-rays. Accordingly, the exposure opening 600may provide the only passage for x-rays out of the collimator 198towards the subject 14.

The exposure ring 604 may be formed on a housing member 606 of thecollimator 198. Generally, the housing member 606 may be part of ahousing 608 that encompasses moving portions of the collimator 198 andallows it to be interconnected with various features, such as the x-raysource 100. The collimator may include the filter 200, such as thefilter 200 d, as discussed above. Further, the collimator 198 may bemounted on the housing 608 which, in turn, is mounted to the x-raysource 100.

In various embodiments, the collimator 198 can include various portionsto allow altering a size or shape of the x-ray beam or cone 108. Forexample, the exposure opening 600 may include a maximum dimension of thex-rays that may exit the collimator 198, such as 3 cm×3 cm. Variousradio opaque leaves, however, that form an axis selection assembly maybe moved relative to the exposure opening 600 to alter the size of acone of x-rays that will pass through the exposure opening 600 and, alsomay position the x-ray beam relative to the exposure opening 600.

With continuing reference to FIG. 9 and additional reference to FIG. 10Aand FIG. 1013, an axis selection assembly (ASA) 626 a, according tovarious embodiments is illustrated. The ASA 626 a is positioned withinthe housing 608 of the collimator 198. The ASA 626 a may include one ormore leaves that are configured to move relative to the exposure opening600 to select a size and/or location of a selected opening 630 to beformed relative to the exposure opening 600. The selected opening 630 isan opening through which the x-rays from the x-ray beam 108 is allowedto pass before exposing the subject 14. The selected opening 630 may beformed before or after the x-ray beam has passed other selected filtersor axes, such as the high speed filter 200 c.

The ASA 626 a that includes a plurality of leaves that are able to moverelative to one another on respective X-axis and Y-axis of movementrelative to the exposure opening 600. For example, as illustrated inFIG. 10A, a first leaf 640 a and a second leaf 640 b may move opposed toeach other and move in an X-axis generally in the direction of thedouble-headed arrow 646. A further pair of leaves may include a thirdleaf 650 a and a fourth leaf 650 b that may move in a Y-axis generallyin the direction of the double-headed arrow 656. Accordingly, the leaves640 and 650 may move relative and/or perpendicular to one another toform the selected opening 630 relative to the collimator exposureopening 600.

The selected opening 630 may be formed in substantially any locationrelative to the exposure opening 600 by selectively moving the leaves640, 650 relative to one another. Movement of the leaves, discussedfurther herein, may be based upon instructions that may be stored in amemory 33 b that may communicate through various communication systems,such as wired, wireless, physical media, or the like, by the controller32 to transmit instructions to move the leaves 640, 650. By moving theleaves, it is understood that the selected opening 630 may be formed inselected shapes, selected sizes, and selected positions relative to theexposure opening 600. Therefore, it is understood that the selectedopening 630, as illustrated in FIGS. 10A and 1013, is merely exemplaryand not intended to limit the possible selected openings.

Each of the leaves 640, 650 may be formed of a selected material, suchas a high Z material (e.g. a material with a high effective Z number orhigh atomic number). For example, the leaves may be formed of lead of aselected thickness. The leaves may be formed so that the detectorsubstantially only receives or detects x-rays that pass through theselected opening 630. Therefore, the leaves 640 and 650 may be moved toselectively create the selected opening 630 at a selected size andposition for exposing the subject 14 to x-rays from the source 100.

The ASA 626 a, including the leaves 640, 650, may include a frameportion 660. The frame 660 may be formed as a single piece, or formed asa plurality of pieces. The frame 660, for example, may be formed as asingle cast piece or member onto which the selected portions of theleaves and other elements are positioned. Alternatively, or in additionto a single member, various pieces may be interconnected such as withwelding, raising, or other fasteners. Additional brackets or fixationpoints may be included with the frame 660, as discussed herein.

Mounted to the frame 660 may be guide rails that assist in guiding theleaves 640, 650. For example, the X-axis leaves 640 may beinterconnected with a first rail 668 and a second rail 670. The rails668, 670 may be fixed to the frame 660 in a selected manner, such aswith rivets, threaded screws, or the like. Further, the rails 668, 670may be substantially parallel to one another. The rails 668, 670 allowthe leaves 640 to move relative to one another substantially bindingfree and in a single plane. Further, the rails 668, 670 assist inmaintaining straight and linear movement of the leaves 640.

The two leaves 640 a, 640 b may be fixed or mounted to leaf carriers 674a and 674 b. Each of the carriers 674 may have fixed thereto one of therespective leaves 640 a, 640 b. Fixation of the leaves to the respectivecarrier 674 may be with braising, rivets, or other appropriate fixationmechanisms. The carriers 674 a, 674 b may extend to cars or slidingmembers 680 a, 680 b, 680 c, 680 d. Each of the carriers 674 a, 674 bmay be fixed to two of the cars that are able to move on the rails 668,670. As the carriers 674 a, 674 b move, the cars 680 a-d may move alongthe respective rails 668, 670 and the carried leaves 640 a, 640 b maymove generally in the direction of the double-headed arrow 646. Theparallel rails 668, 670 allow for smooth and binding free movement ofthe leaves 674 a, 674 b relative to one another, and the frame 660.Further, the parallel rails 668, 670 allow for a driving mechanism 690on a single end, and in various embodiments only the single end, of thecarriers 674 a, 674 b and/or leaves, as illustrated in FIGS. 10A and1013.

The drive mechanism 690 may include various portions such as a motorassembly 692, a sensor assembly, such as a position sensor 694, and adouble lead screw assembly 700. The drive mechanism 690 may operate andbe controlled by the controller 32 with a selected communication system701 that may be provided to control the motor 692 of the drive mechanism690 from the controller 32 and the communication system may receivesensed positions from the sensor 694. Further, the controller 32 may beoperated by a user to selectively operate the motor 692 for variouspurposes during imaging of the subject. Therefore, the drive mechanism690 to move the leaves 640 a and 640 b may be operated in an automaticmanner based upon predetermined instructions, to form the selectedopening 630, manually by a user such as during an imaging procedure, ora combination of both.

The motor 692 may be any appropriate type of motor such as a steppermotor, servo motor, or other appropriate type of motor. Generally, themotor 692 provides rotary motion to a drive shaft 704 which is connectedto the screw assembly 700. The motor 692 may be mounted to a bracket 706that may be fixed to the frame 660 or may be directly fixed to the frame660. A connection portion, such as a split nut 708 may be used toconnect to the drive shaft 704 to the screw assembly 700. The screwassembly 700 may further include a second split nut 710 that connects afirst screw portion 712 to a second screw portion 715.

The first screw portion 712 may threadably engage a carrier holder 714.The carrier holder 714 may be fixed to a bracket or extension 716 of theleaf carrier 674 b. The carrier holder 714 may be fixed to the bracket716 in the appropriate manner, such as with one or more screws 714 a.The screws 714 a, however, may also be provided or included as rivets,nuts, or other appropriate connection mechanisms.

The carrier holder 714 may include an internal thread that is threadedin a first direction. Therefore, as the first screw portion 712 rotateswithin the carrier holder 714 an external thread on the first screwportion 712 may engage internal threads on the carrier holder 714 tomove the leaf carrier 674 b generally in the direction of thedouble-headed arrow 646.

The second screw section 715 may also include an external thread. Thesecond screw section 715, connected to the first screw portion 712through the split nut 710, receives a rotational force from the motor692 via the first screw section 712. A second carrier holder 720 mayinclude an internal thread that is in an opposite direction of theinternal thread of the first carrier holder 714. Therefore, the firstleaf carrier 674 a may move opposite the direction of the second leafcarrier 674 b, although the screw portions 712, 715 are rotating in thesame direction.

The second carrier holder 720 may be fixed to a second extension orbracket portion 722 that extends from the carrier 674 a. The secondcarrier holder 720 may be fixed to the extension 722 with one or morescrews 724 similar to the screw 714 a. The sensor 694 may sense motionor rotation of the screw portion 712, 715 to assist in determining theposition of the leaves 640. The sensor 694 may be connected to thesecond screw portion 715 with a third split nut 728. The position sensor694 may be any appropriate positions sensor, such as an optical shaftencoder including the US Digital® S4T optical shaft encoder (Part No.S4T-300-125-D-B) sold by US Digital, having a place of business inVancouver, Wash., USA.

With continued reference to FIG. 10A and additional reference to FIG.10B, the leaves 650 a and 650 b may be moved in the direction of thedouble-headed arrow 656 on the Y-axis in a manner substantially similarto the leaves 640 a and 640 b. The two leaves 650 a, 650 b may beconnected, individually, to two leaf carriers 780 a, 780 b, in a mannersimilar to the leaves 640 connected to the leaf carriers 674, asdiscussed above.

The leaves 650 may be driven with a drive mechanism 750 similar to thedrive mechanism 690, discussed above. A communication system 752 mayconnect a motor 758 and a position sensor 760 of the drive mechanism 750with the controller 32. The controller 32, therefore, may operate orcontrol both the motor 692 of the drive mechanism 690 and the motor 758of the drive mechanism 750. Operation of the drive mechanism 750 issimilar to the operation of the drive mechanism 690, therefore, itsoperation in part will not be discussed in detail, but disclosed brieflyhere with reference to FIG. 1013.

The drive mechanism 750 may include the motor 758, a sensor 760, and alead screw mechanism 764. Therefore, the motor 758 may be fixed to abracket 766 which is fixed to the frame 660 and/or fixed directly to theframe 660. A drive shaft 770 may be driven by the motor 758 which isconnected to a first screw portion 774 by a split nut 776. The firstscrew portion 774 passes through a third carrier holder 778 tothreadably engage the third carrier holder 778. The third carrier holder778 has internal threads in a first direction to move the leaf carrier780 a to which the leaf 650 b is connected. The leaf carrier 780 a mayinclude an extension 780 b to which the third carrier holder 778 isconnected such as with one or more screws 784. Further, the leaf carrier780 a may extend and interconnect with a car 782 that rides on a thirdrail 786. The leaf carrier 780 a also extends to a car 782 b that rideson a fourth rail 788. The rails 786, 788 may be substantially parallelsimilar to the rails 668, 672, discussed above, to allow for smooth andnon-binding movement of the leaf 650 b with the drive mechanism 750 at asingle end, and in various embodiments only the single end, of the leaf650 b.

The first screw portion 774 is connected to a second screw portion 794with a split nut 796. Other connections, either in addition oralternatively to the split nut 796 may be used, such as welding,adhesive materials, brazing, etc. Therefore, rotational motion of thefirst screw portion 774 is transferred to the second screw portion 794.The second screw portion includes external threads which engage internalthreads in a fourth carrier holder 800. The internal threads in thefourth carrier holder 800 may be opposite those in the internal threadsof the third carrier holder 778. The first and second screw portions 774and 794 may have similar threads and an identical rotational directionof the screw portions 774, 794 will move the respective carrier holders778 and 800 in opposite directions.

The fourth carrier holder 800 may be fixed to the fourth leaf carrier780 b through an extension or projection 804 with one or more screws orother fixation members 806, similar to the fixation members discussedabove. The leaf carrier 780 b may include portions that extend andconnect to two cars 782 c and 782 d so that the leaf carrier 780 b mayride along the rails 788 and 786 generally in the direction ofdouble-headed arrow 656 in the Y axis. As discussed above, the rails786, 788 assist in allowing movement of the leaf 650 a in a smoothing,straight, and non-binding manner.

It is understood the drive mechanisms 690 and 750 may be provided at thesingle ends, and in various embodiments only single ends, of therespective leaves 640, 650 and through the interaction of the leafcarriers 674, 780 with the respective parallel rails 668, 670, 786 and788, allow smooth and non-binding movement of the leaves 640, 650. It isfurther understood, however, that drive mechanisms may be provided atboth ends of the respective leaf carriers to simultaneously drive bothends of the leaf carrier to assist in moving the leaves 640, 650 toselected positions and at a selected rate. In either instance, theleaves 640 a, 640 b may move at a similar or identical speed based oneach other. Similarly, the leaves 650 a, 650 b may move at a similar oridentical speed based on each other. Thus, the selected aperture 630 maybe increased or decreased in size, but have a center 630 a of theselected exposure be substantially unmoved regardless of size or shapeof the selected aperture 630. Accordingly, the selected aperture 630 maybe a square that is 1 inch by 1 inch that has the center 630 a or theselected aperture 630 may be a rectangle that is 1 inch by 2 inches andwould still maintain the center 630 a.

In various embodiments, individual drive mechanisms, similar to thedrive mechanism 690 or the drive mechanism 750, and may include drivemechanisms 691 and 751 (shown in phantom) may be connected individuallyto each of the leaves 640 a, 640 b, 650 a, and 650 b. Thus, each drivemechanism 690, 691, 750, 751 may be used to drive the respectiveindividually each leaf 640 a, 640 b, 650 a, and 650 b on the respectiveX-axis or Y-axis. Each drive mechanism may connect or interact with asingle leaf connector to engage and move the respective leaf. As eachleaf 640 a, 640 b, 650 a, and 650 b moves independently, as operated bythe controller 32, the selected opening 630 may have an independent sizeand the center 630 a may move relative to the frame 660. Thus, it isunderstood that each of the individual leaves 640 a, 640 b, 650 a, and650 b may be driven separately, in a manner similar to that describedabove, with an appropriate drive mechanism to select all of a shape andsize of the selected opening 630 and a location of the center 630 a,such as an alternative center location 630 a′.

Accordingly, the ASA 626 a may be positioned in the collimator 198 toform the selected exposure opening or aperture 630. The ASA 626 a may beincorporated into the collimator 198 in any appropriate manner,including as illustrated in FIG. 9 as discussed above. It is understood,however, that the leaves that form the ASA may be moved in anappropriate manner including those discussed further herein.

In various embodiments, with reference to FIG. 11, the collimator 198may include an ASA 626 b that may include a stage or platform member1620 which may include a stage exposure opening or passage 1624. Thestage exposure opening 1624 may also be fixed in dimension by walls oredges through the stage 1620. The stage exposure opening 1624 may be ofa selected size relative to the exposure opening 600, such as larger,smaller, or the same size. The stage exposure opening 1624 may be largerthan the exposure opening 600 in various embodiments to ensure that allof the exposure opening 600 may be exposed to x-rays, if selected.

The ASA 626 b may be provided in various embodiments, as discussedherein, to selectively size and position an opening formed by leavesrelative to the stage exposure opening 1624. Thus, the stage exposureopening 1624 may define a maximum and/or fixed opening through the stage1620 that may be altered by the ASA 626 b. It is understood, however,that the stage 1620 may not include a small opening, but may includeonly an open or external frame (similar to the frame 660 discussedabove) to which other portions are connected, as discussed herein.

In various embodiments, the ASA 626 b includes a plurality of leaves,including a first leaf 1630, a second leaf 1632, a third leaf 1634, anda fourth leaf 1636. Each pair of the leaves, such as a first pair ofleaves 1630, 1632 and a second pair of leaves 1634, 1636 may operate toadjust the beam of x-rays passing through the stage exposure 1624 in a Xand/or Y axis. For example, the first pair of leaves 1630 and 1632 maymove in an X-axis to change the beam of x-rays in the X axis while thesecond pair of leaves 1634, 1636 may move in a Y-axis to adjust the beamof x-rays through the exposure passage 1624 in a Y axis direction. Asdiscussed further herein, the leaves 1630, 1632, 1634, 1636 may beoperated to adjust a size, a position, or an orientation of a x-ray'sbeam passage through the exposure passage 1624, as selected by a user,programming of the x-ray exposure, selected energy of the x-ray beam, orthe like.

Each of the leaves 1630, 1632, 1634, 1636 may be moved by a selectedmechanism. For example, each leaf may be interconnected with a linearmotor, similar to the linear motor 270 discussed above. For example, thefirst leaf 1630 may be interconnected with a first linear motor 1650,the second leaf 1632 may be interconnected with a second linear motor1652, the third leaf 1634 may be interconnected with a third linearmotor 1654, and the fourth leaf 1636 may be interconnected with a fourthlinear motor 1656. Each of the linear motors 1650, 1652, 1654, and 1656may be operated in a manner similar to the linear motor 270 discussedabove to move the respective leaves 1630-1636 relative to the stageexposure passage 1624.

The linear motors 1650-1654 may be controlled by the control system 32of the imaging system 16; the controller may include the processor 33 athat is designed and/or configured to operate the linear motors1650-1654 and/or execute instruction, such instructions stored on thememory system 33 b. Each of the motors 1650-1656 may be individuallyconnected through various communication lines, such as the respectivecommunication lines 1658, 1660, 1662, and 1664. It is also understoodthat a communication system may be incorporated into the collimator 198to communicate with the controller 32. The communication system mayinclude various wireless communication protocols that may be used towirelessly communicate with the controller 32 to operate the motors1650-1656. As discussed herein, each of the motors 1650-1656 may beoperated independently of one another to move the respective leaves1630-1636 relative to the platform exposure 1624. It is furtherunderstood, however, that the respective motors may be operated as motorpairs. For example, the first motor 1650 and second motor 1652 may beoperated as a pair to move the respective leaves 1630, 1632 relative tothe passage 1624 while the third and fourth motors 1654, 1656 may beoperated as a pair to move the respective leaves 1634, 1636 relative tothe exposure passage 1624. When operated as a motor pair, a singlesignal may be sent to adjust a respective axis of the collimator (e.g.,X axis or Y axis). The single signal may be to adjust the position(e.g., +2 mm). The motor pair may then operate both motors to achievethe adjustment. Generally, the motors 1650-1656 are operated to moverespective leaves to and away from one another as a pair or as the groupof four leaves 1630-1636.

With brief discussion of the first leaf 1630 and the first motor 1650,it is understood that the other leaves and motors may be configuredsubstantially similar to the leaf 1630 and motor 1650 and will not berepeated in detail below. Generally, the leaf 1630 may be formed of aselected material that may be substantially radio opaque. That is, theleaf 1630 may be provided or formed of a material that will not allowx-rays to penetrate or substantially penetrate the leaf 1630 to exposethe x-ray detector through the patient 14. For example, the leaf 1630may be formed of lead having a selected thickness. Any appropriate highZ material, however, may be selected to form the leaf 1630. The leaf1630 may be formed of a material in a selected dimension such that itsmass may be moved at a selected rate by the motor 1650 relative to theexposure opening 1624.

The leaf 1630 may be positioned in a leaf carrier 1670 of the firstmotor 1650. The leaf carrier 1670 may include a first finger 1672 and asecond finger 1674 that extend from a main carrier body 1676. The firstand second fingers 1672, 1674 may define an opening or passagetherethrough and the leaf 1630 may be positioned between the two fingers1672, 1674 in the passage. The leaf 1630 may be fixed within the passagerelative to the fingers 1672, 1674 in any appropriate manner such aswith brazing, an adhesive, a mechanical fixator (e.g., a screw), orother appropriate mechanism.

The leaf carrier 1670 may be mounted to a moving magnet 1680. The movingmagnet 1680 may be positioned over a stationary and/or linear motor coil1682. As discussed above, the stationary linear motor coil 1682 (similarto the stationary linear motor coil 274 discussed above) may be operatedto move the moving magnet 1680 (similar to the magnet 276, discussedabove). It is further understood that various other configurations maybe provided, such as a stationary magnet and moving linear motor coil orthe like. Thus, the leaf carrier 1670 may be mounted to a moving coilthat is moved relative to a fixed magnet.

The leaf carrier 1670 may be fixed to the moving magnet 1680 withvarious mechanisms. For example, a screw or rivet may be positionedthrough a fixation passage 1686 to fix the carrier 1670 to the magnet1680. It is further understood that various pieces, welding, brazing, orthe like may be used to fix the leaf carrier 1670 to the moving magnet1680.

Further, the linear motor 1650 may include linear bearings 1690 on whichthe carrier 1670 moves. The linear bearings 1690 may bear the carrier1670 and the attached moving magnet 1680 as they move. The bearings 1690may also assist in directing movement of the linear motor 1650.Generally, the bearings 1690 may limit a movement of the moving magnet1680, such as generally in the direction of the double-headed arrow1694. The double-headed arrow 1694 may be along the X-axis, as discussedabove, to move the leaf 1630 on the X-axis. A position of the carrier1670 may be determined with a position determining system 1700 includinga read head 1702 and a rail 1704. The read head 1702 may read a relativeor absolute position of the carrier 1670 relative to the rail 1704,similar to operation of the read head 292 and the rail 294, as discussedabove.

Accordingly, the operation of the linear motor 1650 to move the leaf1630 may be similar to operation of movement of the linear motor 270 tomove the filter 260. In particular, the leaf 1630 may be moved to bepositioned into or out of at least a portion of the x-ray beam 108moving along the vector path 110. As discussed further herein, the leaf1630 may be used or operated to block at least a portion of the fullemission of x-rays from the x-ray source 100 to configure or shape thebeam passing through the platform exposure passage 1624.

As discussed above, each of the leaves 1630, 1632, 1634, and 1636 may bemoved as respective pairs and/or moved independently to achieve aselected opening position and/or shape to allow x-rays to pass throughthe platform exposure passage 1624. As illustrated in FIG. 11, theleaves 1632 and 1630 may be the leaves that define the X axis positionof a selected opening 1720. The leaves 1634, 1636 may be moved to changea Y axis position of the opening. As illustrated in FIG. 11, a shape ofthe selected opening 1720 is defined by all of the leaves 1630, 1632,1634, and 1636.

As illustrated in FIG. 11, to allow for each one of the leaves 1630-1634to move relative to one another, the opposing sets of the leaves may beoffset a height relative to the other leaves. As illustrated, the pairof leaves 1630 and 1632 that move in the X-axis may be positionedfurther away from the stage 1620 than the opposed leaves 1634 and 1636that may be positioned closer to the stage 1620 than the X axis leaves1630, 1632. The positioning of the Y axis leaves 1634, 1636 closer tothe stage 1620 may include forming an offset in the leaf carrier 1670 c,1670 d to position them closer to the stage 1620 than the X axis leaves1630, 1632. Alternatively, the X axis carrier 1670 a and 1670 d may beoffset relative to the Y axis leaf carriers 1670 c, 1670 d. Regardlessof the configuration, the leaves opposing one another to form the X andY axis may be configured to allow them to move and be positionedsimultaneously over at least a portion of the stage axis exposure 1624,as illustrated in FIG. 11.

Similar to the selected opening 630, discussed above, the selectedopening 1720 may be any selected shape that may be defined by the leaves1630-1636. Each of the leaves 1630-1636 may be moved independently andindividual, similar to the leaves 640 a, 640 b, 650 a, and 650 bdiscussed above, for the selected opening 1720 to be selected to besquare, rectangular, or other shape depending upon the geometry of therespective leaves 1630-1636. Further, the size of the selected opening1720 may be selected based upon the relative position of the leaves1630-1636.

Moreover, the position of the selected opening 1720, or a center 1720 aof the selected opening 1720, may be selected also based upon theposition of the leaves 1630-1636 relative to the stage exposure openings1624. For example, the stage exposure opening 1624 may be a square, andthe selected opening 1720, and/or the center 1720 a, may be selectivelypositioned in a quadrant of the stage exposure opening 1624 such as alower right quadrant. Further, however, the selected opening may bepositioned in an upper left quadrant, as illustrated in phantom 1720′ bymoving the leaves 1630-1636 to form the selected opening 1720′. Thus,the selected opening 1720′ may be a center 1720 a′ different than thecenter 1720 a of the selected opening 1720. Further, the positioning ofthe leaves 1630-1636 relative to the stage exposure opening 1624 mayselectively make the selected opening 1720 equal to the dimensions ofthe stage exposure 1624 or less than the full opening dimensions of thestage exposure opening 1624.

As discussed above, each of the leaves 1630-1636 may be moved byrespective motors 1650-1656. The position of the leaf carrier 1670, forexample carrying the leaf 1630, may be determined with the read head1702 relative to the rail 1704. As discussed above, the position of theread head 1702 relative to the rail 1704 may be used to determine theposition of the lead carrier 1670 in the manner similar to thedetermining of the position of the linear letter with read head 292relative to the rail 294, as discussed above.

Each of the leaves may be held by respective leaf carriers including aleaf carrier 1670 b to carry leaf 1632, leaf carrier 1670 c to carryleaf 1634, and leaf carrier 1670 d to carry leaf 1636. Each of the leafcarriers 1670 a-1670 d may have respective read heads 1702 a-1702 d thatare fixed to the leaf carriers 1670 a-1670 d and move relative torespective rails 1704 a-1704 d. Communication line or system (e.g.,either wired connections and/or wireless connections) 1658-1664 maycommunicate with a controller 32 to provide instructions to the linearmotor 1650-1656 based upon the determined position of the leaf carriers1670 a-1670 d based upon the read positions of the read heads 1702a-1702 d relative to the rails 1704 a-1704 d.

The movement of the leaf carriers 1670 a-1670 d to move the respectiveleaves 1630-1636 may be based upon a predetermined program or set ofinstructions that are recalled from the memory 33 b. It is furtherunderstood that the memory 33 b may include instructions to determine aplanned or selected movements for forming the selected exposure opening1720 based upon instructions input by a user. Instructions input by auser may be selected or changed during a procedure based upon variousaspects, such as experience of the user, expertise of the user, or otherselected considerations. It is understood, however, that the movement ofthe selected opening 1720 may be predefined and varied relative to thestage exposure 1624 based upon a preselected positioning of the selectedopening 1720. Further, given the four separate motors, each of theleaves may be moved independently (e.g. regarding direction along therespective X- and Y-axes and amount of movement) in the ASA 626 b.

Further, as discussed above, the collimator 198 may be included in theimaging system 16. The imaging system 16 may include the source unit 36that is able or configured to move relative to a selected gantry, suchas the imaging gantry 34. Therefore, as the source unit 36 movesrelative to the gantry 34 and/or relative to the subject 14, the size,shape, and position of the selected opening 1720 relative to the stage1620 may change. The instructions stored in the memory 33 b may be usedto move the selected opening 1720 relative to the stage 1620 as thesource unit 36 moves relative to the gantry 34. Moreover, the controller32 may receive feedback from the respective read heads 1702 a-1702 d todetermine the position of the leaves 1630-1636 to determine furtherand/or appropriate movements of the motors 1650-1656 to position therespective leaves 1630-1636 to form the selected opening 1720 of aselected size and/or position.

The leaves 1630-1636, as illustrated in FIG. 11, are positioned to movefrom one side of the stage aperture 1624 and an edge of the stage 1620.Each of the motors 1650-1656 have portions (e.g. motor coils) fixed on asingle side of the stage aperture and move the respective leaf carriers1670 a-1670 d from the one side towards and over the stage aperture.Generally, as illustrated in FIG. 11, the leaves 1630-1636 may notextend across the stage 1620 from one side to another. It is understood,however, that at least one of the leaves 1630-1636 may extend across thestage 1620.

With reference to FIG. 12, an ASA 626 c is illustrated. The ASA 626 cmay include components of both of the ASA 626 a and the ASA 626 b, asdiscussed above and illustrated in FIGS. 9-11. The ASA 626 c includesthe leaves 640′ and 650′, similar to the ASA 626 a. In the ASA 626 c,however, the leaves 640′, 650′ are moved with linear motors (asdiscussed herein) similar to the linear motors discussed in the ASA 626b. Rather than providing the drive mechanisms 690 and 750, as discussedabove in the ASA 626 a, linear motors are provided to drive the leaves640′, 650′.

The leaves 640′, 650′ may be on leaf carriers 674, 780 as discussedabove, or may be directly connected to respective pairs of parallelrails. Regardless, each one of the leaves may be interconnected with aseparate linear motor to individually move each of the leaves. Each leafmay be interconnected with a single linear motor drive mechanism and therespective pairs of rails to allow for non-binding and smooth movementof the leaves.

As noted above, the ASA 626 c may include portions similar or identicalto the ASA 626 a. With reference to FIG. 12, the ASA 626 c may bemounted to the stage 1620. The ASA 626 c may include the leaves 640′aand 640′b that may move generally in the direction of double headedarrow 646 along the X axis. As illustrated in FIG. 12, the leaves 640′,at only one end or at both ends, may be directly connected to a linearmotor drive mechanism 1760. It is understood, however, that the leaves640′ may be connected to leaf carriers (not illustrated in FIG. 12)similar to leaf carriers 674 discussed above. The ASA 626 c furtherincludes two leaves 650′a and 650′b. The leaves 650′ may be directlyconnected to a second linear drive mechanism 1766, at only one or atboth ends, to move the leaves 650 generally in the direction of doubleheaded arrow 656 in the Y axis. It is understood, however, that theleaves 650′ may also be connected to leaf carriers such, as the carriers780, as discussed above for the ASA 626 a. As illustrated in FIG. 12,and further discussed further herein, however, it is understood thatleaf carriers are not required and that the leaves 640′, 650′ may bedirectly connected to the linear drive mechanisms 1760 and 1766.

As illustrated in FIG. 12, the leaves 640′ and 650′ may be movedrelative to the stage 1620 to form the selected opening 630. The leaves640′, 650′ are connected with the respective drive mechanisms 1760, 1766at only one end or a single end of the respective leaves 640′, 650′. Invarious embodiments, drive mechanisms may be provided at both ends, ifselected. Various bearing and/or rail systems assist in ensuringsmoothing and binding free movement of the leaves 640′, 650′,particularly with the linear motor drive mechanisms connected to onlyone end of the leaves 640′, 650′. Similarly, the drive mechanisms 1760,1766 may be connected to only one end of the leaves 640′, 650′, similarto the connection of the ASA 626 a.

The first leaf 640′a is connected to a first moving coil 1770. Themoving coil may be fixed to the leaf 640′a in any appropriate mannersuch as with an adhesive, welding, or fastener (e.g., rivet, screw, orthe like) or other appropriate connection mechanism. The second leaf640′b is connected to a second moving coil 1772 in a manner similar tothe moving coil 1770 connected to the leaf 640′a. Both of the movingcoils 1770, 1772 move along a common magnet 1774. The common magnet 1774forms a common portion for the drive mechanism 1760 and forms a linearmotor with respect to both of the moving coils 1770, 1772. The linearmotor of the drive mechanism 1760 may operate in a manner similar tothat of the linear motors (e.g. 1650, 1652, 1654,1656 as discussedabove. The moving coils 1770, 1772 of the linear motor drive mechanism1760 may move each of the respective leaves 640′a and 640′b in thedirection of the double headed arrow 646. The respective moving coils1770 and 1772 are connected with the controller 32 with an appropriatecommunication system 1770 a and 1772 a, respectively. The controller 32may operate the linear motor drive mechanism 1760 to move the leaves640′ in the X axis to position and size the selected opening 630 in theX axis. The controller 32 may be manually operated or may executeinstructions using the processor 33 a based on instructions saved andrecalled from the memory 33 b.

The position of the leaves 640′a and 640′b may be determined with aposition sensor 1776, similar to the positions sensors 290 discussedabove. The position sensor 1776 includes a linear or elongated sensor1778 and a first read head 1780 fixedly connected to the moving coil1770 and/or the leaf 640′a to move relative to the sensor 1778. A secondread head 1782 is fixedly connected to the second moving coil 1772and/or the second leaf 640′b to move relative to the sensor 1778. Asdiscussed above, the respective read heads 1780, 1782 may be connectedvia the respective communication systems 1770 a and 1772 a with thecontroller 32 such that a position signal may be transmitted to thecontroller 32 and the controller 32 may be operated to control the drivemechanism 1760 based upon the position signal from the position sensor1776.

Further, the leaves 640′ may be interconnected with bearings or a pairof parallel rails 1784 a and 1784 b. The leaves 640′a, 640′b may bedirectly connected to the rails 1784 and/or interconnected withrespective cars or bearing trucks 1786 a, 1786 b, 1786 c, 1786 d.Therefore, the leaves 640′ may move in a path defined by the rails 1784along the X-axis. Further, the interconnection of the leaves 640′ withthe rails 1784 allows for substantially smooth and non-binding motion inthe X-axis.

The leaves 640′, configured to move in the X-axis, may be offset adistance from a surface 1621 of the stage 1620 greater than a distanceof the leaves 650′. As discussed further herein, the leaves 650′ maymove in the Y-axis which may be substantially perpendicular to the Xaxis. Therefore, to have non-interfering movement of the leaves 640′ inthe X axis and the leaves 650′ in the Y axis, the leaves may bepositioned in different planes so as to not contact one another to allowfor ease of movement of the respective leaves.

The leaves 650′ are connected with the drive mechanism 1766 at one endof the leaves 650′. Similar to the leaves 640′, the leaf 650′a isfixedly connected to a third moving coil 1790 and the fourth leaf 650′bis fixedly connected to a fourth moving coil 1792. The third and fourthmoving coils 1790, 1792 move along a single and common magnet 1794 toform the linear motor drive mechanism 1766. Again, each of the movingcoils 1790, 1792 are connected with the controller 32 with respectiveand appropriate communication systems 1792 a and 1790 a. Again, it isunderstood that the communication systems 1770 a, 1772 a, 1790 a, and1792 a may be wired communication systems, wireless communicationsystems, physical media transmission systems, or other appropriatecommunication systems. The controller 32 may operate the drive mechanism1766 to move the leaves 650′ in a manner similar to that described aboveto operate a linear motor.

Further, the controller 32 may receive position signals from a positionsensor 1796 associated with the drive system 1766. The position sensor1796 may include a single scale sensor 1798. A third read head 1800 maybe fixed to the moving coil 1790 and/or the third leaf 650′a. A fourthread head 1802 may be fixed to the fourth moving coil 1792 and/or thefourth leaf 650′b. Both of the read heads 1800, 1802 may move along thesensor 1798 to provide a common reference position sense and positionsignal for the drive system 1766. The position signal may be transmittedto the controller 32 with the respective communication systems 1790 aand 1792 a. The controller 32, therefore, may know or determine theposition of the leaves 650′a and 650′b with the position signal from theposition sensor 1796.

The drive mechanism 1766 is connected to one end of the leaves 650′. Theleaves 650′, however, may be interconnected with a bearing systemincluding a third rail 1804 a and a fourth rail 1804 b. The rails 1804a, 1804 b may form a second pair of rails or bearings that issubstantially perpendicular to the bearing rails 1784 a, 1784 b. Theleaves 650′ may directly engage the rails 1804 and/or may be connectedwith cars or moving bearings or trucks 1806 a, 1806 b, 1806, and 1806 d.Regardless, the rails 1804 allow for substantially smooth andnon-binding movement of the leaves 650′.

The ASA 626 c, therefore, may include leaves substantially similar oridentical leaves to the 640, 650 of the ASA 626 a and drive mechanismssimilar to the drive mechanisms of the ASA 626 b. The leaves 640′, 650′of the ASA 626 c may be moved to form the selected opening 630 in amanner similar to the leaves 640, 650 of the ASA 626 a with thealternative motors or drive mechanisms 1760 and 1766. The leaves 640′,650′ may, as illustrated in FIG. 12, extend from one side of the stage1620 to a second side of the stage 1620 and may cross the stage aperture1624. For example, the rails of the rail pairs 1784, 1804 are spacedacross the stage aperture 1624 from one another. Thus, the leaves 640′,650′ may span or cross the stage 1620. Further, the leaves 640′, 650′may be interconnected with moving magnets rather than moving coils, asdiscussed above. Accordingly, it is understood, that the ASA 626 c maybe controlled with instructions to form the selected opening 630 similarto the manner of the ASA 626 a as discussed above. It is furtherunderstood, however, that the individual connections of the coils 1770,1772 to the leaves 640′, 650′ may allow for independent movement (e.g.amount and/or direction) of each of the leaves 640′a, 640′b, 650′a, and650′b relative to one another and the stage 1620.

The collimator 198, as illustrated in FIG. 9 may also include filters inaddition to the high speed filter 200, according to various embodimentsincluding the high speed filter 200 c, as illustrated in FIG. 9.Additional filters may include filtering elements or portions forvarious features such as tailoring the beam spectrum to optimize imagingperformance when acquiring the image data. The filters may be providedin a multiple element or position filter assembly 2000. The filterassembly 2000 may include a plurality of filter positions or locations2010, including individual positions 2010 a, 2010 b, 2010 c, 2010 d,2010 e, 2010 f, 2010 g, and 2010 h. The filter locations 2010 may beformed as passages or openings in a filter carrier or plate 2014. Ateach of the filter positions 2010, a selected filter material may beincluded. The filter material may be placed in a void or opening formedin the filter carrier 2014. The filter material may be opaque ortransparent to various wavelengths or energies. For example, the filterposition 2010 a may include a filter material such as copper, tin,silver, aluminum, alloys thereof, layered materials, or otherappropriate material with a selected Z reference value that limits orselected a type or energy level of x-rays for passing through theexposure opening 600 of the collimator 198. Further, one or more of thefilter positions 2010 may not include any filter material, thusproviding a void, to form an unfiltered passage through the filtercarrier 2014 for x-rays or other emissions. Certain filter materials ormaterials may be provided that do not substantially interact with x-raysso that the filter position acts as a void even if a material is withinthe path of the x-rays.

The filter plate 2014 may be formed as a substantially circular platemember having exterior perimeter teeth 2020. The teeth 2020 allow thefilter carrier 2014 to be rotated around a central axis 2022 on an axleor spindle 2024 to position one of the filter positions 2010 relative tothe exposure opening 600. The external teeth 2020 may be engaged by aspindle gear 2030 having external teeth that is driven by a motorassembly 2032. The motor assembly 2032 may be controlled by thecontroller 32 through a communication system 2034. The communicationsystem may be any appropriate communication system, such as a wired,wireless, or other appropriate communication system. The motor assembly2032 may include any appropriate type of motor such as a servo motor orstepper motor. The motor assembly 2032 may drive the external gear 2030to rotate the filter carrier 2014 according to a selected plan orinstructions, such as instructions that may be stored on the memory 33b.

The filter assembly 2000 may further include a position sensor assembly2040 that may communicate with a controller 32 through a communicationline 2042. The position sensor 2040 may include a spindle gear 2044 thatis engaged on the exterior teeth 2020 of the filter carrier 2014. As thefilter carrier 2014 rotates, the spindle gear 2044 may also rotate andthe sensor 2040 may determine a relative or absolute position of thefilter carrier 2014 based upon movement of the spindle gear 2044.

The position sensor 2040 may include an optical or mechanical encoder,such as the US Digital® S4T optical shaft encoder. Based upon theposition sensor 2040, the motor 2032 may be operated to position aselected one of the filter elements in a selected one of the filterpositions 1020 a-h relative to the exposure opening 600. The filtercarrier 2014 may spin or rotate on the axis 2022 on the axle 2024 thatis selectively fixed to the frame 660. The frame 660 that may hold theASA 626 a may be fixed relative to the exposure opening 600. It isunderstood, however, that the axle 2024 may be fixed to any appropriateportion of the collimator 198, including the housing 608. Therefore, theposition of the filter carrier 2014 may be rotated relative to theexposure opening 600 by operating the motor 2032. Similarly, the highspeed filter 200 c may be mounted on the frame 660.

With continued reference to FIG. 9 and additional reference to FIG. 13,a multiple element or position filter assembly 2100 is illustrated. Thefilter assembly 2100 may include a filter carrier 2110. The filtercarrier 2110 may include the plurality of filter positions 2010 a-2010h, similar to the filter positions discussed above of the filterassembly 2000. Again, the filter carrier 2110 may be rotated around theaxis 2022 on an axle 2130 to position one of the filter positions 2010a-h relative to the exposure opening 600, to position the filterposition 2010 relative to the exposure opening 600.

The filter assembly 2100, however, may be driven by a drive assemblysimilar to the drive assembly of the high speed filter 200 c, asdiscussed above and illustrated in FIG. 5 and FIG. 6. The drive assemblyfor the filter assembly 2100, therefore, may include the carry gear 360(not illustrated in FIG. 13) which holds or carries the filter carrier2110, as discussed above. The carrier gear 360 may be driven by the belt364 that is driven by the drive gear 366 on the shaft 370. The shaft 370may be driven by the motor assembly 374. As discussed above, the motorassembly 374 may include a motor within a housing 376 that may becontrolled by the controller 32 with the communication or control line380. The motor assembly 374 may be controlled to position a selected oneof the filter positions 2010 relative to the opening 600 in a mannersimilar to that discussed above. The different positions 2010 may beidentified with various sensors, such as index sensors and the like todetermine the position of the filter plate 2110. The filter assembly2000, however, may be operated in a non-continuous motion operation,therefore absolute position sensors may be used to determine which ofthe filter positions 2010 a-h are aligned with the exposure opening 600.

The plurality of filter potions 2010 a-h of the filter assembly 2000 andthe filter assembly 2100 generally allows one of the filter positions2010 a-h to be positioned relative to the exposure opening 600 for aselected period of time. Therefore, the filter plate or carrier 2014 or2110 generally may not rotate continuously during an imaging procedure.Accordingly, the motor assembly and sensors may be selected based uponthe reduced amount of motion and may include absolute position sensorsto determine a position of the filter carrier, including the filterpositions 2010 relative to the opening 600.

With reference to FIG. 14, a filter assembly 2200 is illustrated. Thefilter assembly 2200 is illustrated positioned relative to the stage1620 of the ASA 626 b illustrated in FIG. 11. It is understood, however,that the filter assembly 2200 may be positioned relative to anyappropriate portion of the collimator 198. The filter assembly 2200 mayinclude a grid or patterned filter carrier 2210 that includes aplurality of filter positions or openings 2220 a-2220 i. The filtercarrier may move in a plane and generally in two axes, e.g. X-axis andY-axis.

Each of the filter positions 2220 may include a different filtermaterial and/or be open to not filter any transmission through theexposure opening 1624. The filter carrier 2210 may be moved relative tothe exposure opening 1624 and/or the opening 600 of the collimator 198by movement along parallel rails. A first set of parallel rails includesa first rail 2230 a and 2230 b. The first set of parallel rails 2230 maybe fixed to the stage 1620. A number of cars, including four cars 2232a-2232 d may move along the rails 2230 generally in the direction of thedouble-headed arrow 2236.

Mounted to the first set of cars 2232 may be a plurality of additionalcars 2240 a-2240 d as the first set of cars 2230 move in the directionof double-headed arrow 2236, they move the second set of cars 2240 inthe same direction. Movable relative to the second set of cars 2240 maybe a second set of rails including a third rail 2250 a and fourth rail2250 b. The second set of rails 2250 may generally move in a directionof double-headed arrow 2254. The filter carrier 2210 may be fixed to thesecond set of rails 2250 in any appropriate manner, such as withwelding, adhesives, or fasteners.

As the second set of rails 2250 moves in the direction of double-headedarrow 2254, the filter carrier 2210 also moves in the direction of thedouble-headed arrow 2254. Further, because the rail members 2250 areinterconnected with the first set of cars 2232, the frame carrier 2210also moves in the direction of double-headed arrow 2236 in a selectedmanner. Therefore, the filter carrier 2210 may be moved relative to theexposure opening 1624 in the stage 1620 and/or the exposure opening 600in the direction of either double-headed arrow 2236 or 2254, such as xand y directions.

Movement of the cars 2232 or the rails 2250, relative to the cars 2240,may be formed in any appropriate manner. For example, as discussedabove, lead screws driven by selected motors (e.g., servo motors orstepper motors), linear motors, or other appropriate motor drivemechanisms may be used to move the respective cars 2232 and/or the rails2250. In this way the filter carrier 2210 may be moved relative to theexposure opening 1624.

According to various embodiments, the frame carrier 2210 may includeonly a single row of filter positions, rather than a grid. In a singlerow, the frame carrier need only move in a single axis, such as onlytranslate along the X-axis. In such a configuration, the frame carriermay resemble a ladder where a filter position is between each rung ofthe ladder. The ladder filter carrier may also reduce the number ofrails and/or cars riding on rails needed to move the ladder. Forexample, the ladder may be moved on a single pair of parallel rails inthe X-axis. The ladder frame carrier may be moved in two directions,however, along the X-axis. The movement of the ladder filter carrier maybe powered by any selected appropriate motor, such as linear motors asdiscussed above. The linear motor may be positioned to move the ladderfilter carrier relative to the exposure opening 600. Further, the ladderfilter carrier may be moved based on instructions or control from thecontroller 32.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

What is claimed is:
 1. An assembly for an imaging system, comprising: acollimator assembly having an exposure opening; a multiple filterposition carrier having a plurality of filter positions; a first filtermedium positioned in a first filter position of the plurality of filterpositions; a drive system having a drive motor connected to the multiplefilter position carrier to selectively move the multiple filter positioncarrier to at least one of the first filter position or the secondfilter position to be aligned with the exposure opening.
 2. The assemblyof claim 1, wherein at least one filter position of the multiple filterpositions includes a void or filter material that does not effect thex-rays that pass the at least one filter position; wherein the multiplefilter position carrier has at least eight filter positions; wherein thedrive system is configured to drive each of the eight filter positionsto be aligned with the exposure opening.
 3. The assembly of claim 2,wherein the multiple filter position carrier is round; wherein each ofthe eight filter positions are formed near a perimeter of the multiplefilter position carrier; wherein the multiple filter position carrier isturned around a central axis extending through the multiple filterposition carrier by the drive system.
 4. The assembly of claim 3,wherein the drive system further includes a spur gear having externalteeth on a perimeter of the spur gear and the spur gear is driven by thedrive motor; wherein the multiple filter position carrier has externalteeth on the perimeter of the multiple filter position carrier; whereinthe external teeth of the spur gear engage the external teeth of themultiple filter position carrier to drive the multiple filter positioncarrier.
 5. The assembly of claim 4, further comprising: a positionsensor having a second spur gear; wherein the second spur gear engagesthe external teeth of the multiple filter position carrier; wherein themultiple filter position carrier spins the second spur gear of theposition sensor to generate a position signal regarding movement of themultiple filter position carrier.
 6. The assembly of claim 5, furthercomprising: a controller configured to receive the position signal fromthe position sensor and generate a control signal to operate the motorto move the multiple filter position carrier to position a selectedfilter position aligned with the exposure opening.
 7. The assembly ofclaim 3, wherein the drive system further includes a drive belt and acarrier gear; wherein the drive belt is driven by the drive motor and isoperably connected to the carrier gear.
 8. The assembly of claim 7,further comprising: a position sensor having a first portion fixed tothe carrier gear and a second portion connected to a spindle aroundwhich the multiple filter position carrier rotates around the centralaxis; wherein the positon sensor generates a position signal based on aninteraction of the first portion and the second portion.
 9. The assemblyof claim 8, further comprising: a controller configured to receive theposition signal from the position sensor and generate a control signalto operate the motor to move the multiple filter position carrier toposition a selected filter position aligned with the exposure opening.10. The assembly of claim 1, further comprising: a first pair of rails;and a second pair of rails; wherein the multiple filter position carrierincludes each of the plurality of filter positions in a grid format andthe multiple filter position carrier moves in a substantially x and ydirection relative to the exposure opening.